Scrubbers DO NOT export Phosphorus

[xerophyte_nyc]

Now that I have your attention :-)

Full disclosure - I have an ATS, I have posted my build in this forum, and I have contributed to the knowledge base here. This thread is not about bashing any method. It is about trying to understand what is really happening, so that we can better our aquaria.

Abbreviations: P=total phosphorus, Po=organic phosphorus, Pi=inorganic phosphorus

Over at Nano-Reef (http://www.nano-reef.com/topic/319561-refugiums-dont-export-nutrients/)we had a great, informative, entertaining, sometimes confrontational, but overall a very thought provoking thread on the concept that Macroalgae in a reef tank (in a fuge, or ATS) can NOT export net phosphorus. The origin of the Nano-Reef thread is one titled "Algae - What's Under The Hood..." (http://www.thereeftank.com/forums/f77/algae-whats-under-the-hood-how-does-it-do-and-what-cant-it-do-198321-32.html)over at The Reef Tank forum (you have to join to view). I won't re-hash everything in those 2 threads, and I encourage others to go through those on your own - they are tedious at times, but enlightening.

At first it seems impossible. How does an ATS not export P? What about all that algae I harvest every week that is thrown out, it has P in it, right? Yes it does...but during that week of growth, the algae has been dumping as much, or maybe even more, equivalent mass of Po (which we cannot measure) into the tank as it has been consuming Pi, feeding the bacteria that use the Po to make more Pi, which then feeds the algae, and so on...it is a cycle. The way I just described it is obviously very simplified, but for our purposes it will be suitable. There is research documenting this. The best one I have seen quantifies the net P biomass lost as 8% of the total algae P biomass - but this 8% comes during an incubation test period of about 4-5 hrs if I recall, and the algae were in a state of starvation so they were conserving Po. The references are in the above threads, I can post them later.

Algae will reach a homeostatic balance of Pi input and Pi export based on how much Pi is in the tank. It is like an algal survival mechanism. If it sucks up all the Pi available, it would starve (=not good). The algae won't keep extracting Pi at a steady rate until there is none left. It will balance its use depending on availability. It is mathematically impossible for an ATS to reduce total P in a tank.

There are other benefits to an ATS. But for this discussion, I want to only focus on the P export aspect of it.

What can the ATS do then, with regards to P? It can create a competitive situation whereby Pi is utilized by the ATS in favor of the nuisance algae in the display, which esthetically at least is a benefit. It can also act as a buffer, if you will. If you are a heavy feeder, the algae will increase its rate of Pi use, again preventing assimilation into nuisance algae, to a limited degree of course.

This leads us back now to the issue of the Po that the algae is leaking into the tank. On the one hand, Po does not really harm the tank inhabitants. It can even be viewed as a food source for coral. But it is also a preferred food source for bacteria. It is less energetically expensive for a bacteria to break P bonds in dissolved Po, than it is for them to break the bonds of Po that is bound to the rock or substrate (these are calcium-P bonds). Bacteria will utilize the high levels of dissolved Po in favor of the calcium-bound Po. What does this mean? The substrate and live rock can now more easily bind excess Po floating around. Depending on how big your P sink is (how much rock, how much sand), eventually, without outside help, it will be saturated ---> tank crash?

Water changes help removing Po. Siphoning and detritus removal take Po with it. A skimmer can be good at removing Po. Somewhere, in between all these methods of Po export, there is a balance that can be reached with an ATS in the system.

But the danger is if we rely to heavily on the ATS, then we are reaching a saturation point more quickly.

Now let's assume we are doing water changes, skimming, etc. along with an ATS in an adequate enough manner where Po becomes an overall algae limiter in the system (via reduced bacterial conversion of Po->Pi)...then theoretically, all things being equal, the ATS has reached maximum efficiency. This is good. It means that we have reached a point where the ATS will work the best in your favor to compete with nuisance algae.

I have seen numerous instances on this forum where algae growth seems to be reduced, or changes quality and color, and we keep pushing more light and more flow. Maybe this is incorrect - maybe in some of those cases, they reached the system max because they are exporting Po correctly? Maybe we need to reduce ATS growth because the screen/ light/ flow are exceeding the algal capacity? I would love to say, let's feed more, but then we are just making it harder to deal with all the Po.

I don't have nearly all the answers. I do have lots of questions, as I'm sure others here will too. Given this info about how P cycles in a tank, let's discuss and strategize.

[kotlec]

So when we are measuring 0.00 on Hanna, what does this means in real world ? At the same time I never was 100% free of gha.

[Garf]

Hmm. You cannot remove P from a system and still have the same amount left in the system. Therefore a net export, which is what we are after. If people (like me) choose to feed more then good. Great start to a thread by the way. Looking forward to other views.

[SantaMonica]

A few readings of marine biology nutrient studies, or especially, phycology assimilation studies will change your mind :)

It would be impossible for algal biomass to grow without consuming net P. Just ask the biofuel people who have to add millions of pounds of P to their water in order to grow sufficient mass. Your model would mean that their P would remain constant.

Couple of corrections:


Bacteria will utilize the high levels of dissolved Po in favor of the calcium-bound Po.

Your Po (known as POC: Particlate Organic Carbon; also known as "food") does not bind to rocks; only your Pi (orthophosphate, or DIP: Dissolved Inorganic Phosphorus) does. And aerobic bacteria does not consume this bound P from the rocks until the P redissolves, due to a lowered pH.


Water changes help removing Po. Siphoning and detritus removal take Po with it. A skimmer can be good at removing Po.

Yes, these do remove food particles. But when are you going to put them back in? If dosing aminos or vitamins, you'll need to dose more. If feeding liquid or powdered coral foods, you'll need to feed more.


I have seen numerous instances on this forum where algae growth seems to be reduced, or changes quality and color, and we keep pushing more light and more flow. Maybe this is incorrect

You do not add light if the growth becomes nutrient limited, i.e., bright yellow. Flow, yes. Iron, yes.


Maybe we need to reduce ATS growth because the screen/ light/ flow are exceeding the algal capacity?

This is the reason for the reduced screen size recommendation; to keep what nutrients there are confined to long gha instead of spread out over large areas of brown slime.


maybe in some of those cases, they [algae] reached the system max because they are exporting Po correctly?

Algae don't export your Po (known as POC: Particlate Organic Carbon; also known as "food"), they only export your Pi (orthophosphate, or DIP: Dissolved Inorganic Phosphorus).

[Garf]

Probably the best response I've seen to be honest. However, this does not explain the accumulation of dissolved organic carbon. When you stop exporting through a skimmer, for instance, it is extremely easy (through bubbles on a screen) to form a foam. This indicates to me that the exudates from algae and corals are not being used as fast as previously thought, hence an excess. This excess then can (in certain circumstances) fuel dino's and other unpleasant natural phenomena.

[xerophyte_nyc]

So when we are measuring 0.00 on Hanna, what does this means in real world ? At the same time I never was 100% free of gha.

Hanna and other kits are only measuring inorganic phosphate, which is consumed so quickly when it is available that testing kits are not really accurate. There is no good way for hobbyists to measure organic P sources, unfortunately.

[Garf]

Hanna and other kits are only measuring inorganic phosphate, which is consumed so quickly when it is available that testing kits are not really accurate. There is no good way for hobbyists to measure organic P sources, unfortunately.

And dino's for example can tap into the organically bound P. therefore making inorganic readings defunct.

[xerophyte_nyc]

Garf said, you cannot remove P from the system and have the same amount left.

Technically that is correct. The instant that algae is flushed down the toilet, there is some P that is bound within the algae being exported. At that point, the bacteria in the tank suddenly lost a source of food, because the algae was providing Po all week long. Some bacteria will die, liberating more Po. Some bacteria will now switch to using the P bound in rock for food. The sum of all that bacterial activity is more net Pi back into the water, so that algae can grow again. The cycle continues with back and forth swings until it is in balance again. Since we continually feed our tanks, there is always more P incoming. If you stopped feeding, then you would see that the algae won't grow as fast, it will just gain biomass in harmony with bacteria to match the nutrient levels in the tank.

[Garf]

Took a while to get to grips with this. I agree, got an old thread relating to the exudates of algae (which are basically a carbon dosing [sugars]). And all carbon dosing methods correctly state that you must export (skim).

[xerophyte_nyc]

A few readings of marine biology nutrient studies, or especially, phycology assimilation studies will change your mind :)


Maybe, maybe not :confused:



It would be impossible for algal biomass to grow without consuming net P. Just ask the biofuel people who have to add millions of pounds of P to their water in order to grow sufficient mass. Your model would mean that their P would remain constant.


The moment the algae is harvested, yes technically there is P being thrown out. But from the time that growth started from a freshly harvested screen, for that week while algae was growing, there was MUCH more P going in and out of the algae biomass. And there is excess Po being shed into the water. This Po forms detritus and pollutes the substrate and binds to Calcium. This is the bad part because we cannot measure it, only after the substrate is full are there problems. As aquarists and ATS proponents we need to understand this better, and account for it in our husbandry.


And aerobic bacteria does not consume this bound P from the rocks until the P redissolves, due to a lowered pH.

This part doesn't even matter (for now).




Yes, these do remove food particles. But when are you going to put them back in? If dosing aminos or vitamins, you'll need to dose more. If feeding liquid or powdered coral foods, you'll need to feed more.

It is a conundrum. We can't have great food from Po and not have to account for it binding to calcium in the substrate and rock at the same time.




Algae don't export your Po (known as POC: Particlate Organic Carbon; also known as "food"), they only export your Pi (orthophosphate, or DIP: Dissolved Inorganic Phosphorus).

What about all those amino acids and all the other great things the ATS adds to the water? Bacteria will get to this before coral will. It is better to feed coral particulate food that we add, than to rely on waste products. I'm not saying that the dissolved food is a bad thing - I'm just suggesting there is too much of it, which is bad for the tank long term without another means of export like skimming, water changes, detritus removal.

Bacteria are the primary source of Pi in aquaria. They process dissolved nutrients, liberating Pi. The dissolved nutrients come from food, waste, and algal waste. They can also digest the P bound to rock (but that is much harder for it to do). The Pi liberated by bacteria is what fuels algae. It is a tightly knit cycle. In the oceans, we have abyssal plains and geothermal processes that bind the phosphate away. In an aquarium, we do not. We have skimmers, water change, etc.

I'm not discounting scrubbers. I just want us to better understand how to manage our aquariums, by accounting for all this organic P.

I have literature and links that describe the phosphate cycle, etc. I will provide them later for everyone to read and understand. Looking forward.

[Garf]

Exactly. The oceans have there own export mechanisms. Replicating this in a glass box means skimming to a greater or lesser extent.

[celtic_fox]

IMO, it sounds like the argument is being made more complicated than it needs to be.

If, (and I say 'if', because I really don't know how accurate it is) you get a bacterial die off in some sort of relation to the amount of algae exported, it is still a net export of P (from the system as a whole).

It's a fact that you are removing some sort of P in the physical mass of the algea. If some bacteria die, it's not like they are lost forever. They grow back as the algea comes back, and during that growth P is used again, and then some is exported again. Over and over, etc, etc.

Does it really mater that there is some P getting back into the system from bacterial die off when it's just going to fuel the next growth cycle?

And just a thought - this may be another reason to perhaps only clean one half of the screen or screens at a time?

[xerophyte_nyc]

IMO, it sounds like the argument is being made more complicated than it needs to be.

If, (and I say 'if', because I really don't know how accurate it is) you get a bacterial die off in some sort of relation to the amount of algae exported, it is still a net export of P (from the system as a whole).

It's a fact that you are removing some sort of P in the physical mass of the algea. If some bacteria die, it's not like they are lost forever. They grow back as the algea comes back, and during that growth P is used again, and then some is exported again. Over and over, etc, etc.

Does it really mater that there is some P getting back into the system from bacterial die off when it's just going to fuel the next growth cycle?

And just a thought - this may be another reason to perhaps only clean one half of the screen or screens at a time?

Let's assume there is a net P export every week when you harvest algae. Let's also assume that you are feeding about the same amount each week. Why isn't the algae shrinking each week then? The P levels in the tank should be diminishing every week until you get to a point there is not enough P left to support algae. But this does not happen.

Where is all the P? It is in the dissolved P that you don't see. It is becoming trapped in the tank - specifically, in the sand substrate or rock. And when the rock fills up?

[xerophyte_nyc]

Does it really mater that there is some P getting back into the system from bacterial die off when it's just going to fuel the next growth cycle?

Yes it does, for the reasons already mentioned. All this extra P has to go somewhere. My point is that we have to better understand this process, so that we can avoid problems with our tanks. A scrubber does not replace a skimmer - if anything, it makes a skimmer more important, to help handle the extra invisible Po load.

[xerophyte_nyc]

Link to original work: The Oceanic Phosphorus Cycle (http://pmc.ucsc.edu/~apaytan/publications/2007_Articles/PaytanMcLaughlin_ChemRev_2007_107_563TheOceanicPCy cle.pdf)

Some excerpts below:


"The organic and inorganic particulate and dissolved forms of phosphorus undergo continuous transformations. The dissolved inorganic phosphorus (usually as orthophosphate) is assimilated by phytoplankton and altered to organic phosphorus compounds....Continuing the cycle, the inorganic P is rapidly assimilated by phytoplankton while some of the organic P compounds can be hydrolyzed by enzymes synthesized by bacteria and phytoplankton and subsequently assimilated...Dissolved inorganic and organic P is also adsorbed onto and desorbed from particulate matter sinking in the water column moving between the dissolved and the particulate fractions."

Heterotrophic bacteria are responsible for much of the DOP hydrolysis and conversion back to DIP

Much of the DIP uptake takes place in the sunlit upper zone of the water column (euphotic zone), where marine photosynthesis takes place. ; hydrolysis of organic P (both particulate and dissolved) to DIP occurs throughout the water column.

P is generally preferentially remineralized from particulate organic matter in the water column. More specifically, certain organic P compounds are preferentially remineralized in sinking particulate matter and the hydrolysis of organic P occurs throughout the water column, though more prevalently in shallow depths.



I realize this is an ocean model and does not translate directly to our tanks, but this is important nonetheless. We also do not have appreciable levels of phytoplankton in our tanks, but algae in our tanks would represent the consumers of Pi.

Santa Monica, you mentioned that a review of marine biology would make me understand this differently. Please share with us your info about marine microbiology. I shared with you some of mine. I have more. Maybe I am mistaken.

Please understand, I am absolutely not trying to be confrontational. I want to get to the bottom of this, for my tank's sake. When I first started reading about scrubbers and their benefits, it sounded great. I made my own ATS. But then recently I was exposed to more info about the phosphate cycle which has changed my thought process. The message that an ATS replaces a skimmer, IMO, is a fallacy that continues to be perpetuated. A skimmer should, in theory, improve an ATS tank by helping eliminate excess Po. I don't even run a skimmer yet, but I will be soon. I have an ATS, some carbon and purigen. Based on the evidence, I am polluting my tank with invisible Po.

It would be irresponsible of me not to share this insight with the ATS community. I can't even take credit for it. It came to me via another thread on another forum.

Let's take this info and think about how to modify our routines to make our aquaria better. There is a Po overload in scrubbed tanks. The challenge is to find the sweet spot whereby we can optimize an ATS to compete with nuisance algae, while also exporting Po efficiently. We all have mesotrophic tanks. They are not nutrient poor. But we can still grow beautiful coral. An ATS is really the only good method I know of to out-compete nuisance algae, in a non ULNS tank. We just have to manage the extra Po.

EDIT: Here is a link to my scrubber (http://algaescrubber.net/forums/showthread.php?2400-The-scrubber-is-now-active), on this forum.

[Nick28]

extra phosphorus will accumulate but it binds to calcium and metals then

calcium dissolves and releases it back (you add new sand) and the scrubber takes up extra p and heavy metals as it can adjust its ratios

only PO4 is a problem not phosphorus

I suppose a heavily fed rockless,sandless tank setup with just a scrubber could get to the bottom of such an argument?

[xerophyte_nyc]

extra phosphorus will accumulate but it binds to calcium and metals then

Yes, calcium is very efficient at doing this. I think that's sort of the idea behind a remote DSB - it acts as a phosphate sink, except that it is hard to get detritus to accumulate in a remote location. But when is the substrate full? I don't know, nobody knows, until it is too late.



calcium dissolves and releases it back

This only happens at low pH. I don't recall exactly, I think in the 7's. This is not typical of our tanks, nor should it ever be attempted. In our tanks, the only real natural mechanism for release of bound P is via bacterial degradation. And they will only do this when dissolved P levels are too low to supply their needs. Or you can replace live rock on occasion (who would really do this?)...or replace the substrate - much easier to do. Note: silica sand does not chemically bind P the same as calcium based sand like araonite.



(you add new sand) and the scrubber takes up extra p and heavy metals as it can adjust its ratios

It would be better to remove some sand periodically, then replace it with fresh new substrate. Rinse, repeat. Metal uptake of an ATS is definitely a benefit. Remember, I never said an ATS does not have benefits. I'm just focusing specifically on its ability to process P.



only PO4 is a problem not phosphorus

It doesn't matter which one is present, because it will all tie right into the bacterial-algae cycle. A little too much Po, then bacteria make more Pi which feeds algae until equilibrium. A little too much Pi, then algae will feed Po to bacteria until equilibrium. Using GFO has limited effect, since it is also competing with algae. If GFO was being used aggressively, then the algae biomass would decrease to an extent, to match the nutrient level of the tank until a new equilibrium is reached. But GFO is not enough to substantially reduce overall P in the tank - if it was, we would all be rocking crazy GFO reactors and have zero algae with SPS calcifying 2 ft a year!


I suppose a heavily fed rockless,sandless tank setup with just a scrubber could get to the bottom of such an argument?

Yes it would. Such a tank should theoretically not be able to support algae growth, although there would be nothing for processing nitrogen, but I get your point. That's where ULNS trends towards, with bare bottom. Minimal algae. But that's not what most of us have, or even want. Not me, at least. Too much work to do lots of water changes and siphoning detritus all the time.

[xerophyte_nyc]

I have also seen mention of the thought that a waterfall scrubber is nothing more than an efficient detritus trap, fostering an environment for nutrient collection and algae growth. Like a fancy filter sock. Maybe we can just illuminate a filter sock under a sump drain and get a similar response?

Anyone know why GHA always grows well on a scrubber? Why not bryopsis, or Chaeto?

I have a completely unproven theory that a scrubber selects for specific bacteria that attach to the screen, like how GHA seems to dominate. This bacteria grows together with GHA and forms part of 3d matrix. Within the bacterial biofilm, there is efficient nutrient transfer going on locally. Po to Pi to Po, right on the screen. Some Po escapes and goes to the tank. When I dip my scrubber screen into my tank to let pods escape, I notice an oily residue that washes away. Is this detritus that is decomposing? Is it part of a bacterial biofilm?

I know this all may be much to take in. I was in denial at first. But I did not let that cloud my mind. I tried to keep emotion out of it. It took me a few days to wrap my brain around these concepts. I cannot find a good argument to refute the evidence. As soon as we, as a group, come to grips with the P cycle, we can then come up with new strategies for our tanks. There are also cases where we see scrubbers failing, or changing colors, or having unpredictable results. Maybe the P cycle has something to do with it all? Again, I don't have all the answers.

[celtic_fox]

Let's assume there is a net P export every week when you harvest algae. Let's also assume that you are feeding about the same amount each week. Why isn't the algae shrinking each week then? The P levels in the tank should be diminishing every week until you get to a point there is not enough P left to support algae. But this does not happen.

Where is all the P? It is in the dissolved P that you don't see. It is becoming trapped in the tank - specifically, in the sand substrate or rock. And when the rock fills up?

Seems like some assumptions in there just to try and win an argument. (I'm not saying you aren't or won't eventually be proven right. I'm just saying you're making some assumptions that don't necessarily happen.) We do see people with less growth when they feed less, and more when they feed more. Sometimes it happens right away, sometimes it takes a cycle or two for the effect to become apparent.


Also, can you re-explain this? (Seriously, I'm missing something in your statement. And just for the record, I'll be the first to admit, I don't understand all of this, so this is a straight question, not an argument.)


It is less energetically expensive for a bacteria to break P bonds in dissolved Po, than it is for them to break the bonds of Po that is bound to the rock or substrate (these are calcium-P bonds). Bacteria will utilize the high levels of dissolved Po in favor of the calcium-bound Po. What does this mean? The substrate and live rock can now more easily bind excess Po floating around.

If bacteria is utilizing the high levels of dissolved Po in favor of the calcium-bound Po, then where is the "excess Po" that you're refering to coming from? (Are you saying the calcium-bound Po is floating around?)

[Nick28]

Yes, calcium is very efficient at doing this. I think that's sort of the idea behind a remote DSB - it acts as a phosphate sink, except that it is hard to get detritus to accumulate in a remote location. But when is the substrate full? I don't know, nobody knows, until it is too late.

i never found a DSB to be a phosphate sink its constantly moving like gears on a machine problems arise when there is no anaerobic region do to too much flow or too shallow (too much oxygenation).



This only happens at low pH. I don't recall exactly, I think in the 7's. This is not typical of our tanks, nor should it ever be attempted. In our tanks, the only real natural mechanism for release of bound P is via bacterial degradation. And they will only do this when dissolved P levels are too low to supply their needs. Or you can replace live rock on occasion (who would really do this?)...or replace the substrate - much easier to do. Note: silica sand does not chemically bind P the same as calcium based sand like araonite.

faster at a lower ph and at deeper levels, however there is biological activity occuring on the surface of every grain of sand there are acidic enzymes and carbonic acid released from bacterial respiration ,plus fish waste releases acids that must be neutralized anyone who has had an aquarium for years will eventually need to add aragonite sand as it dissolves grains get finer.





It would be better to remove some sand periodically, then replace it with fresh new substrate. Rinse, repeat. Metal uptake of an ATS is definitely a benefit. Remember, I never said an ATS does not have benefits. I'm just focusing specifically on its ability to process P.

If P ever did become a problem say from an unclean water source you could use calcium carbonate or calcite in a media bag like GFO it wont be as effective but will be cheaper






Yes it would. Such a tank should theoretically not be able to support algae growth, although there would be nothing for processing nitrogen, but I get your point. That's where ULNS trends towards, with bare bottom. Minimal algae. But that's not what most of us have, or even want. Not me, at least. Too much work to do lots of water changes and siphoning detritus all the time.


the scrubber can process nitrogen, basically setting up an empty tank with nutrients and a scrubber will yield the same effect as a tank with rock and sand if this is a problem the P would have no where to settle or bind, it would accumulate in the water column and cause algae or cyano problems in the display tank that are unsolvable by the ATS alone.

The ocean is not an aquarium

the ocean gets rid of P and Silica and toxins (say from human input) by burying which eventually makes its way to magma pools high tempertures breakdown most compounds to raw elements. then they come out on land (High phosphourus and high silica lava) in some cases or get deposited in new rock.

the ocean can not export any other way. The ocean can hold or temporarily remove N and P by algae growth and N can be broken down by denitrification.

our export would be like the ocean launching a space shuttle full of nutrients into space (our ATS total removal from the ecosystem) then bringing them back during feeding time only.

[Nick28]

I have a completely unproven theory that a scrubber selects for specific bacteria that attach to the screen, like how GHA seems to dominate. This bacteria grows together with GHA and forms part of 3d matrix. Within the bacterial biofilm, there is efficient nutrient transfer going on locally. Po to Pi to Po, right on the screen. Some Po escapes and goes to the tank. When I dip my scrubber screen into my tank to let pods escape, I notice an oily residue that washes away. Is this detritus that is decomposing? Is it part of a bacterial biofilm?

there is also N released by this residue and it has an acceptable N:P ratio for later reabsorption after cleaning. You also don't want N and P to be absolutely zero which is impossible anyways.

[xerophyte_nyc]

i never found a DSB to be a phosphate sink its constantly moving like gears on a machine problems arise when there is no anaerobic region do to too much flow or too shallow (too much oxygenation).

A functional DSB with good circulation and movement of pore volume should in theory work very well. Also, depending on the size of the DSB and other export methods being used, a DSB could be sinking in P for many, many years until there is trouble. The problem is there is no good way to quantify this process in our hobby.




faster at a lower ph and at deeper levels, however there is biological activity occuring on the surface of every grain of sand there are acidic enzymes and carbonic acid released from bacterial respiration ,plus fish waste releases acids that must be neutralized anyone who has had an aquarium for years will eventually need to add aragonite sand as it dissolves grains get finer.

Correct. This is happening on a small scale, every minute, every hour. I don't know exactly how this contributes to the overall P, in relation to the dissolved portion already present via other biologic activities.




If P ever did become a problem say from an unclean water source you could use calcium carbonate or calcite in a media bag like GFO it wont be as effective but will be cheaper

If the unclean water source has Po, then GFO will do nothing, but a calcium bag would help - how much, I don't know. Calcium and GFO are binding different forms of P.

If there is Pi being inputted via water, then the GFO must also compete with algae in the tank, so it will not get it all.




the scrubber can process nitrogen, basically setting up an empty tank with nutrients and a scrubber will yield the same effect as a tank with rock and sand if this is a problem the P would have no where to settle or bind, it would accumulate in the water column and cause algae or cyano problems in the display tank that are unsolvable by the ATS alone.

The ATS is out-competing the nuisance algae for Pi. The excess P in the tank is in organic form. If there are not enough bacteria to consume it, or if carbon is limiting (which it will be at some point, why do ATS tanks trend to alkalinity?), then the excess is deposited as detritus. If carbon is not limiting (let's say you dose vodka or CO2) then bacteria will be able to process all that Po but there will be a massive bacterial bloom. Since in most ATS tanks carbon can be a limiter, it means that some Po is leftover.

In essence, an ATS is a Po doser. What I am looking to find out is where is the sweet spot, at what point do the negatives outweigh the positives. It is far more effective to remove Po right away (skimmer, frequent water change, remove detritus) before it ever gets to the bacteria. Algae is the last one to get the P. That is inefficient.



The ocean is not an aquarium

Absolutely. I eluded to this in one of my earlier posts. We have to be careful when extrapolating marine science to our aquaria. Unfortunately, hobby literature is lacking so sometimes all we have is marine research.






our export would be like the ocean launching a space shuttle full of nutrients into space (our ATS total removal from the ecosystem) then bringing them back during feeding time only.

Interesting analogy :cool:

[xerophyte_nyc]

Seems like some assumptions in there just to try and win an argument. (I'm not saying you aren't or won't eventually be proven right. I'm just saying you're making some assumptions that don't necessarily happen.) We do see people with less growth when they feed less, and more when they feed more. Sometimes it happens right away, sometimes it takes a cycle or two for the effect to become apparent.

I really am not trying to prove anything, this is not about starting or winning an argument. My only vested interest, as with everyone else, is to come up with strategies to make our tanks beautiful with preferably less labor. I feel that when I invested time and energy into researching an ATS and how it helps a tank, there wasn't full disclosure.

The assumption I made about feeding the tank equally every day was done simply in an effort to try and make all this more understandable. Yes there are a lot of things being left out. Especially that phosphorus exists in many forms. For me to lump them all into Po or Pi only is not accurate, I know that, but it helps to better illustrate the concept that the total phosphorus in the tank is not really ever changing unless Po is also being exported.

P that we add into the tank is mainly organic Po. We are providing food for bacteria (after coral, fish get to it), not algae. When the bacteria eat, they liberate Pi, which then feeds the algae. More food into tank--> more Pi. Less food into tank-->less Pi.

When the ATS is harvested, the net P removed at that moment is less than the net P that was imported during that entire week of growth. Check the reference below. The researchers discovered that on average 8% of algae's P biomass is excreted during a 2-4 hour period of a light cycle, and this was at low nutrient levels where growth is slower. Using those values, if your ATS is lit 12 hours, 25-50% of the algae P biomass is excreted per day. In 2-4 days, the net export is equal to net import. After a week???

To be more efficient at true nutrient export, a scrubber would have to be cleaned every day. But this would result in reduced algae growth in time as the algae-bacteria re-equilibrate themselves to a lower nutrient level. You would end up chasing things with too much effort to make it worthwhile.





Also, can you re-explain this? (Seriously, I'm missing something in your statement. And just for the record, I'll be the first to admit, I don't understand all of this, so this is a straight question, not an argument.) If bacteria is utilizing the high levels of dissolved Po in favor of the calcium-bound Po, then where is the "excess Po" that you're refering to coming from? (Are you saying the calcium-bound Po is floating around?)

It can get confusing. It took me time to grasp it. The excess Po exists because there is not enough bacterial biomass to get to all of the Po in the water column. Some of it will precipitate as detritus. It is not much on a day to day basis. But it will build up in time. That's why skimming, water changes, etc. are helpful - they remove the dissolved Po. It is competition with bacteria. If you compete well, bacteria population dwindles, they make less Pi (so less food for algae), and they can start to use some of that calcium-bound P. It all comes down to understanding and manipulating bacteria. They are in control.

Here are some links for further "enrichment":

Phosphate Cycle image, with means of export (http://www.nano-reef.com/gallery/image/38858-phosphate-circles-final-graaphic/)

Adsorption of phosphate on calcium carbonate (http://www.aoml.noaa.gov/flbay/millero1.html)

Thread on reef central with Randy Holmes Farley discussing phosphate and calcium (http://www.reefcentral.com/forums/showthread.php?p=15968762)

Excretion of Dissolved Organic Phosphorus in Tropical Brackish Waters (http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_55-56/010023665.pdf) - this one shows the 8% Po excretion per 2-4 hrs

[Nick28]

keep in mind i'm not being belligerent with my posts




The ATS is out-competing the nuisance algae for Pi. The excess P in the tank is in organic form. If there are not enough bacteria to consume it, or if carbon is limiting (which it will be at some point, why do ATS tanks trend to alkalinity?), then the excess is deposited as detritus. If carbon is not limiting (let's say you dose vodka or CO2) then bacteria will be able to process all that Po but there will be a massive bacterial bloom. Since in most ATS tanks carbon can be a limiter, it means that some Po is leftover.

In essence, an ATS is a Po doser. What I am looking to find out is where is the sweet spot, at what point do the negatives outweigh the positives. It is far more effective to remove Po right away (skimmer, frequent water change, remove detritus) before it ever gets to the bacteria. Algae is the last one to get the P. That is inefficient.

Scrubbers don't lower alkalinity (minimal effect at best) high calcification rates do, (and this tends to happen on tanks run with scrubbers) bicarbonate is absorbed, HO- is released this hits the surface and binds with CO2 to form a new bicarbonate ion.

new carbon is brought in by phyto at the surface and fish food.

organic p is rapidly converted to inorganic p by microorganism on every surface of the aquarium (these guys don't live long either they are constantly being eaten and regrown)

organic p is harmless it wont be a problem until things start dieing (say a power outage) and you will get inorganic p relatively quickly

any unabsorbed vitamins, aminos and nutrients that contain P released by the scrubber will turn into inorganic p and be reabsorbed. The scrubber will not throw the same quanity of these compounds out only what it can based on nutrients available.

phyto, zooplankton, coral and fish are organic P








Interesting analogy :cool:

thanks :D

[Floyd R Turbo]

My head doth explodeth

[xerophyte_nyc]

keep in mind i'm not being belligerent with my posts

I know. No worries, even if someone does get upset. I understand.




Scrubbers don't lower alkalinity (minimal effect at best) high calcification rates do, (and this tends to happen on tanks run with scrubbers) bicarbonate is absorbed, HO- is released this hits the surface and binds with CO2 to form a new bicarbonate ion.

new carbon is brought in by phyto at the surface and fish food.

When I mentioned trending to alkalinity, I meant that pH goes up. I did not mean the dKh/ alk. In my own ATS tank, I can't get pH to go any lower than 8.48. It goes from 8.48-8.64. I am assuming that bacteria is using up CO2.



organic p is rapidly converted to inorganic p by microorganism on every surface of the aquarium (these guys don't live long either they are constantly being eaten and regrown)

organic p is harmless it wont be a problem until things start dieing (say a power outage) and you will get inorganic p relatively quickly

organic P by itself is harmless, correct. But it doesn't just float around. Not all of it is consumed. Some will become detritus or bound to substrate. That is the bad part - we can't measure this. If the substrate fills up and there are no more binding spots, we have ourselves a problem. This could take many years depending on other variables. Or maybe not.



any unabsorbed vitamins, aminos and nutrients that contain P released by the scrubber will turn into inorganic p and be reabsorbed. The scrubber will not throw the same quanity of these compounds out only what it can based on nutrients available.

phyto, zooplankton, coral and fish are organic P

There is not enough bacterial biomass to consume all the excess Po. Some of that Po floats around unused. If there was no excess, we would not see detritus accumulate. But detritus is there. Look in your tank in areas where there is low flow.

To make algae grow, we have to dump food in, then the algae dumps food back out. Then we harvest a fraction of the net total P that has been in flux during that whole week. It is completely inefficient. The only benefit, as far as P is concerned, is that it out-competes the nuisance algae. That is it. An ATS does not export net P. It is mathematically impossible. What we see is an illusion. Algae grows because we are feeding the bacteria. It is far more efficient, if P export is the goal, to attack the Po.

What I want to figure out, with the help of the folks on this forum, is what is the minimum amount of ATS needed in a tank where it will still effectively outcompete nuisance algae, and still allow us to realistically export Po via skimming, water changes and detritus removal.

Maybe the guidelines that we have are good enough, I don't know. What I do know is that an ATS absolutely does not replace a skimmer. They do very different things. It would be more accurate to say that an ATS makes a skimmer more important, not less.

But if you really want an ATS, then a skimmer might be your best friend (along with water change and detritus removal)

[xerophyte_nyc]

My head doth explodeth

Happened to me too. Once your neurons settle in, it will get better.

[Ace25]

Way to many unscientific 'assumptions' in this thread and we all know what 'assuming' leads to. If you do A then that can equal B, C, or D, but if you do B, then A and C are the outcomes, but if you do D... etc etc... bottom line, way to many variables to make any type of conclusion. One of my tanks (the one doing good and only ran an ATS since day 1) goes against pretty much everything that has been said in this thread in regards to bacteria, skimmers, PO4 not being exported, etc, which makes me not believe any of the 'facts' being stated in this thread.

[Skinnysloth]

When the ATS is harvested, the net P removed at that moment is less than the net P that was imported during that entire week of growth. Check the reference below. The researchers discovered that on average 8% of algae's P biomass is excreted during a 2-4 hour period of a light cycle, and this was at low nutrient levels where growth is slower. Using those values, if your ATS is lit 12 hours, 25-50% of the algae P biomass is excreted per day. In 2-4 days, the net export is equal to net import. After a week???


Help me understand this statement. I may be missing something. So if 8% of the algae's P biomass is excreted during 2-4 hours of a light cycle, then in 2-4 days it would have excreted 100% of its biomass. So at this point, you're saying the amount of P that went into the algae had all been excreted. Does the algae just stop uptaking P, while excreting 8% every 2-4 hours. In the 2-4 hour period, it 'sequestered' 92% and is that all the P that it ever needs without uptaking any more additional P? What maybe confusing me is, I don't know what % of the biomass is taken up in the form of P during that 2-4 hours. If the algae intakes 10% of its biomass in P and then excretes 18%, there would be a net loss of 8% of P from the algae, but by that account, the algae is just dumping P into the system.

Unless you're saying, 8% is excreted, but the algae replenishes the lost P by absorbing 8%, then we have a net gain of 0. Then P is never sequestered in the algae but is just transported through it? Admittedly, I only glanced at that research paper, so I'm not sure what is meant by 8% excreted in the whole grand scheme of things.

Great topic and discussion by the way.

[celtic_fox]

Does anyone have a link to the mineral breakdown of GHA (or something very similar)? I was unable to find it with a few searches and I'm trying to at least look productive at work... I'm curious to see exactly what we are exporting.

I'd always assumed P was used somewhere in the creation of the algea mass and thus was being removed... and the Pi and Po left in the tank would (eventually) be reshuffled by, and find a new balance with, the organisms still in the tank.

[Nick28]

When I mentioned trending to alkalinity, I meant that pH goes up. I did not mean the dKh/ alk. In my own ATS tank, I can't get pH to go any lower than 8.48. It goes from 8.48-8.64. I am assuming that bacteria is using up CO2.

Hydroxide being released from the algae when lights are on raises the PH, also maybe you drip kalk?


organic P by itself is harmless, correct. But it doesn't just float around. Not all of it is consumed. Some will become detritus or bound to substrate. That is the bad part - we can't measure this. If the substrate fills up and there are no more binding spots, we have ourselves a problem. This could take many years depending on other variables. Or maybe not.

It won't be a problem, accumilating detritus is caused by lack of flow or poor biological filtration( which some people choose to siphon in bare bottom tanks). I noticed detritus accumilating in my bare bottom skimmer only tank. upon adding a hang on dsb (CPR fuge ;no light) and shallow sand bed in the display removing the skimmer and making an ATS ,detritus vanished. (obviously not saying the skimmer caused it but it wasn't doing a good job). Any organic p from detritus will rapidly become inorganic p and yes, it will bind to a calcium substrate. if your tanks PH plummeted a mass release would occur. Then again everything would be dying as well.

this is what i was talking about before about substrate dissolution, this keeps unbinding p slowly releasing inorganic P into the water where it can be taken up by the scrubber. A scrubber in a tank with lets say a P saturated substrate (although never truly saturated cause its always exchanging) will end up fixing itself to take up more P


There is not enough bacterial biomass to consume all the excess Po. Some of that Po floats around unused. If there was no excess, we would not see detritus accumulate. But detritus is there. Look in your tank in areas where there is low flow.

it does not need to be taken up as biomass as the bacteria will use other components of organic P and reject inorganic P. There is also a lot of bacteria on the algae and screen so when you clean it you remove small amounts.


To make algae grow, we have to dump food in, then the algae dumps food back out. Then we harvest a fraction of the net total P that has been in flux during that whole week. It is completely inefficient. The only benefit, as far as P is concerned, is that it out-competes the nuisance algae. That is it. An ATS does not export net P. It is mathematically impossible. What we see is an illusion. Algae grows because we are feeding the bacteria. It is far more efficient, if P export is the goal, to attack the Po.

using biopellets or vodka for skimming obviously works but it is a waste of money compared to a properly setup ATS. It also can cause bleaching by starving the tank. A tank should have low inorganic p not organic P

[Nick28]

Does anyone have a link to the mineral breakdown of GHA (or something very similar)? I was unable to find it with a few searches and I'm trying to at least look productive at work... I'm curious to see exactly what we are exporting.

I'd always assumed P was used somewhere in the creation of the algea mass and thus was being removed... and the Pi and Po left in the tank would (eventually) be reshuffled by, and find a new balance with, the organisms still in the tank.
3930

unfortunatly, it would be hard to come to a conclusion here and nutrients can still vary a little.

[Garf]

Gonna throw a spanner in the works here. The 8% excreted P (linked earlier) is not of total biomass, it's of P. UPTAKE. So the remaining 92% is translated to growth or storage, hence removed when harvested.

[kotlec]

When the ATS is harvested, the net P removed at that moment is less than the net P that was imported during that entire week of growth. Check the reference below. The researchers discovered that on average 8% of algae's P biomass is excreted during a 2-4 hour period of a light cycle, and this was at low nutrient levels where growth is slower. Using those values, if your ATS is lit 12 hours, 25-50% of the algae P biomass is excreted per day. In 2-4 days, the net export is equal to net import. After a week???


There is very big mathematical or logical error in this calculation. Most likely both.

[RkyRickstr]

boom.. there goes my brans.

[xerophyte_nyc]

Way to many unscientific 'assumptions' in this thread and we all know what 'assuming' leads to. If you do A then that can equal B, C, or D, but if you do B, then A and C are the outcomes, but if you do D... etc etc... bottom line, way to many variables to make any type of conclusion. One of my tanks (the one doing good and only ran an ATS since day 1) goes against pretty much everything that has been said in this thread in regards to bacteria, skimmers, PO4 not being exported, etc, which makes me not believe any of the 'facts' being stated in this thread.

I provided some evidence discussing the phosphate cycle. There are many variables, things we don't understand. What cannot be argued is that algae grow to suit their nutrient level. The mere fact we are able to grow algae very well on a screen signifies a high enough nutrient level. It is also a fact that algae are shedding Po, although the rate of this is subject to interpretation. This shedding is higher when nutrient levels are higher in the tank, thereby contributing to the total P. This adds to detritus.

Please share with us your tank set-up and maintenance routine. There's no reason we should not have beautiful tanks with an ATS, that is not what I'm insinuating. I want to know how to handle the extra P that is shed by the algae. The extra Po is the price we pay for having an ATS.

[xerophyte_nyc]

Help me understand this statement. I may be missing something. So if 8% of the algae's P biomass is excreted during 2-4 hours of a light cycle, then in 2-4 days it would have excreted 100% of its biomass.

It's like a "revolving door". As an adult you eat many pounds of food per week, much of it is excreted, you did not gain much mass during that week. Algae takes in lots of P, but also lets a lot back out. When the screen is cleaned off, algae grows fast and the gain in biomass is clearly measurable - but from minute-to-minute and hour-by-hour there will be small fluctuations up and down where the Po excreted is higher and lower, depending on what is going on in the water column, i.e. did I just feed my fish.

This is related to photosynthesis and the Calvin cycle. I don't want to go there, LOL! There is plenty of info on the web. Lots of phosporylation and de-phosphorylation as ADP+Pi is converted to ATP, back and forth, in and out of cells. Not to mention algae growth, formation of cell structures, proteins, starches, etc.

Algae reach max growth at levels below the nutrient levels in the tank, at this point the decay rate is greater. This probably happens as we get closer to the end of the week. There would probably be less Po loss if the ATS were cleaned sooner, before growth gets closer to the equilibrium.

It's like putting a hole on the side of a bucket. You keep filling the bucket with water but it never reaches the top, some is always leaking out the hole. Algae keeps consuming Pi, and dumps out Po. As algae grows, that hole in the bucket slowly gets higher (up and down along the way) until it stops and/ or lowers. When you harvest, you dump the bucket, but what about all that water that leaked out along the way??

It's called Liebig's Law of the Minimum (http://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum)





Great topic and discussion by the way.

Yes, really gets us thinking

[xerophyte_nyc]

Hydroxide being released from the algae when lights are on raises the PH, also maybe you drip kalk?

I have dripped, very little (<1 tsp per 2 gal top-off) and I add acetic acid. But even when I don't add kalk for 2 weeks, pH doesn't drop. I even recalibrated my pH probe. Inhabitants seem healthy otherwise.




this is what i was talking about before about substrate dissolution, this keeps unbinding p slowly releasing inorganic P into the water where it can be taken up by the scrubber. A scrubber in a tank with lets say a P saturated substrate (although never truly saturated cause its always exchanging) will end up fixing itself to take up more P

It doesn't make logical sense to use an ATS to take up P, since it will be giving so much of it back. An ATS seems more suitable as a P buffer, not as a means of export.




A tank should have low inorganic p not organic P

Correct. But organic P will lead to more Pi, you just may not be able to measure that uptick in Pi because it is consumed so quickly. If there is enough Pi to feed good algae growth, then some of that Pi could also be inhibiting coral calcification.

[xerophyte_nyc]

Gonna throw a spanner in the works here. The 8% excreted P (linked earlier) is not of total biomass, it's of P. UPTAKE. So the remaining 92% is translated to growth or storage, hence removed when harvested.

Right, it is 8% of P biomass.

Biological processes are not usually linear, they are circular. I don't know how else to explain it. See Liebig's Law (http://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum), and my other examples earlier. Liebig's Law is not a perfect analogy, but I can't find one better. Liebig has to do with limiters.

Imagine a revolving door with 10 slots but only half are filled. It keeps turning. 2 new people are added, 1 leaves. It keeps spinning. Again someone is added, and someone leaves. Keep adding one for one. At the end of the day, a lot of new people were added to the door in total, and almost the same amount left. At any one time it looks like only one person left - that one out of 5 is 20%. At the end of the day depending on the rate of addition and subtraction, there could have been tons of people moving in and leaving as well.

EDIT: In the case of the algae, we are talking 8% not 20%. The exact number is meaningless. There are also studies out there which show a 40% Po excretion. The revolving door is algae metabolism. People coming in and out represent P flux. When more people stay in the revolving door, than when we started, that represents a net biomass gain. You can gain almost 20% biomass by adding one person to the door, but how much P was recycled along the way?

Does this analogy make sense?

[xerophyte_nyc]

There is very big mathematical or logical error in this calculation. Most likely both.

Please see the post above I just made to Garf.



I have tried just as hard as you guys to find flaws, but I can't really find any. Oh the irony. I was on the other end of this "battle" not too long ago.

[xerophyte_nyc]

Gonna throw a spanner in the works here. The 8% excreted P (linked earlier) is not of total biomass, it's of P. UPTAKE. So the remaining 92% is translated to growth or storage, hence removed when harvested.

Actually you may be onto something here!...let me take a closer look. And to make matters more confusing, it is actually the bacterial biomass that it is being compared to

EDIT: That was a good catch Garf! My interpretation, correct me if I'm wrong - this study is a set-up devoid of nutrients and there is no detritus. They are seeing that even in a state of relative starvation, algae are still leaking Po - this leakage represents 8% of bacterial biomass. The authors are treating this as equivalent to measuring the bacterial uptake.

"we can compare phytoplankton P-excretion rate to PO4-P uptake rate, and get the P-excretion rate relative to microbial biomass which is evaluated by particulate phosphorus"

As far as I can tell then, this study is still demonstrating that algae in a 4-hr period are leaking enough Po to make it a significant amount in relation to bacterial biomass - remember, bacterial biomass is much less than algae.

I don't think this changes my previous revolving door analogies. What do you think, Garf?

[Nick28]

It doesn't make logical sense to use an ATS to take up P, since it will be giving so much of it back. An ATS seems more suitable as a P buffer, not as a means of export. yes it does, there are plenty of people with properly setup scrubbers that don't experience the problems of phosphate.





Correct. But organic P will lead to more Pi, you just may not be able to measure that uptick in Pi because it is consumed so quickly. If there is enough Pi to feed good algae growth, then some of that Pi could also be inhibiting coral calcification.

no there is an equilibrium in the water if pi is released and gets bound to a coral skeleton it will come off into the water column as the water phosphate is lowered

SantaMonica has stated P coming out of rocks many times. I find this to be true as eventually my rocks exploded with branching and scrolling coraline growth something that I have never seen before with a skimmer.

.03 and .00 phosphate is common.

[Skinnysloth]

There is very big mathematical or logical error in this calculation. Most likely both.

I see I was not the only one that thought it didn't make sense.



It's like putting a hole on the side of a bucket. You keep filling the bucket with water but it never reaches the top, some is always leaking out the hole. Algae keeps consuming Pi, and dumps out Po. As algae grows, that hole in the bucket slowly gets higher (up and down along the way) until it stops and/ or lowers. When you harvest, you dump the bucket, but what about all that water that leaked out along the way??

It's called Liebig's Law of the Minimum (http://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum)


I understand that concept, but your statement, 'In 2-4 days, the net export is equal to net import. After a week???' seems to indicate algae stops importing P, while it continues to leak 8% of it. But in your analogy, you keep filling the buck with water, but it never reaches the top, implies that the algae continues to import P and whatever amount that was sequestered when you harvest (dump the bucket) gets exported out the system. You asked, what about the water/P that leaked out? In reply, I ask, what about all the P that was thrown out? It may be leaking some of it back into the water, but is it not continuing to use the other 92% or sequestering it?

We may achieve an equilibrium with the rate of phosphate introduction via food and export/sequestration via ATS, skimmer, GFO, sand, rock, etc., but I still don’t understand how the ATS is not exporting P when you harvest it. Let’s say that P is continually recycled during the Calvin cycle, so the P is neither gained nor lost. Even with the leakage of 8%, if the algae is able to grow faster than the 8% loss, are we not taking additional P from the water to power the Calvin cycle in the new algae growth/cells and getting rid of P when we harvest?

[Amphiprion]

Like in the thread on NR, we've known this stuff for a while, so I can't necessarily argue that. Some of FD's facts weren't quite right, like saying algae don't actually store P (they do) and, naturally, he wouldn't admit that, but by and large, that is what happens. We argued this back on RC years ago. What I think he has portrayed completely inaccurately is the actual rate in which this stuff happens on a typical time scale in our systems. I think he was very misleading, before conceding a bit, that this takes a good long while to happen and it isn't just 5-10 years, either. I think in reasonably healthy systems that this can take a good long time, more like 15-20 years, barring other disasters. He was also inaccurate about live rock, somehow thinking that it was able to purge itself when it ends up doing the exact same thing (considering many people end up "cooking" older live rock to prevent this). Even in his more ideal system with no sand and just live rock, large skimmer, and water changes, the rock will eventually be an issue--I've had that happen before, too. He'd still have to tear down the rocks the redo things eventually, possibly even more often than someone with a long-term sink for it. That being said, which would you rather do? Have a relatively trouble free tank for a long time, allowing nature to do its job or one that requires maintenance constantly? I've been down the latter path and I will never do it again, considering that missed maintenance one time could be absolutely crucial. As I said before, it is one of the most expensive, labor-intensive ways to go about doing this. We know that scrubbers can still grow corals (despite what was being said)--exactly how much "extra" growth is there to be gained from reef levels of phosphate? I'm not convinced it is terribly more significant and the tradeoffs, in my experience, are worse (i.e. starvation). If it really is that much more significant, I'd have to see it quantified to really lean in that direction. Of course, it would have to be appropriately quantified in an aquarium to begin making comparisons, since we'd need a baseline in our tanks to even start comparing to natural reefs. I think all of this would've fallen on deaf ears in the other thread, though.

In that same vein, there was a study I read a few months back that showed an increase in growth (at a reduced skeletal density, which decreases inversely with P concentration) with ever so slightly elevated P and that lack of growth is not a reasonable nor accurate sign of eutrophication/enrichment. If I can find it, that may be one blow against a portion of this argument. Not that I think that high P is good by any means, but that keeping it at extremely low seawater levels may not be completely necessary. That being said, I don't think FD's tank is as free of phosphate as he'd like to believe or have anyone else believe, either, all things considered.

Beyond that, I think there is more going on than meets the eye here and that it is being oversimplified, not accounting for other mechanisms (Occam's razor, I know, but probably not an unreasonable line of thought). I may have to consult some classmates and professors who are actually Ph.Ds in marine sciences in the hope that they may know more or have more insight. None, unfortunately, are chemical oceanographers, so I'm not sure how much they would be able to help in our exact situation. Shouldn't hurt to ask, though.

[xerophyte_nyc]

Very well said, thank you!


Like in the thread on NR, we've known this stuff for a while, so I can't necessarily argue that. Some of FD's facts weren't quite right, like saying algae don't actually store P (they do) and, naturally, he wouldn't admit that, but by and large, that is what happens. We argued this back on RC years ago. What I think he has portrayed completely inaccurately is the actual rate in which this stuff happens on a typical time scale in our systems. I think he was very misleading, before conceding a bit, that this takes a good long while to happen and it isn't just 5-10 years, either. I think in reasonably healthy systems that this can take a good long time, more like 15-20 years, barring other disasters. He was also inaccurate about live rock, somehow thinking that it was able to purge itself when it ends up doing the exact same thing (considering many people end up "cooking" older live rock to prevent this). Even in his more ideal system with no sand and just live rock, large skimmer, and water changes, the rock will eventually be an issue--I've had that happen before, too. He'd still have to tear down the rocks the redo things eventually, possibly even more often than someone with a long-term sink for it. That being said, which would you rather do? Have a relatively trouble free tank for a long time, allowing nature to do its job or one that requires maintenance constantly? I've been down the latter path and I will never do it again, considering that missed maintenance one time could be absolutely crucial. As I said before, it is one of the most expensive, labor-intensive ways to go about doing this. We know that scrubbers can still grow corals (despite what was being said)--exactly how much "extra" growth is there to be gained from reef levels of phosphate? I'm not convinced it is terribly more significant and the tradeoffs, in my experience, are worse (i.e. starvation). If it really is that much more significant, I'd have to see it quantified to really lean in that direction. Of course, it would have to be appropriately quantified in an aquarium to begin making comparisons, since we'd need a baseline in our tanks to even start comparing to natural reefs. I think all of this would've fallen on deaf ears in the other thread, though.

In that same vein, there was a study I read a few months back that showed an increase in growth (at a reduced skeletal density, which decreases inversely with P concentration) with ever so slightly elevated P and that lack of growth is not a reasonable nor accurate sign of eutrophication/enrichment. If I can find it, that may be one blow against a portion of this argument. Not that I think that high P is good by any means, but that keeping it at extremely low seawater levels may not be completely necessary. That being said, I don't think FD's tank is as free of phosphate as he'd like to believe or have anyone else believe, either, all things considered.

Beyond that, I think there is more going on than meets the eye here and that it is being oversimplified, not accounting for other mechanisms (Occam's razor, I know, but probably not an unreasonable line of thought). I may have to consult some classmates and professors who are actually Ph.Ds in marine sciences in the hope that they may know more or have more insight. None, unfortunately, are chemical oceanographers, so I'm not sure how much they would be able to help in our exact situation. Shouldn't hurt to ask, though.

[xerophyte_nyc]

I see I was not the only one that thought it didn't make sense.



I understand that concept, but your statement, 'In 2-4 days, the net export is equal to net import. After a week???' seems to indicate algae stops importing P, while it continues to leak 8% of it. But in your analogy, you keep filling the buck with water, but it never reaches the top, implies that the algae continues to import P and whatever amount that was sequestered when you harvest (dump the bucket) gets exported out the system. You asked, what about the water/P that leaked out? In reply, I ask, what about all the P that was thrown out? It may be leaking some of it back into the water, but is it not continuing to use the other 92% or sequestering it?

We may achieve an equilibrium with the rate of phosphate introduction via food and export/sequestration via ATS, skimmer, GFO, sand, rock, etc., but I still don’t understand how the ATS is not exporting P when you harvest it. Let’s say that P is continually recycled during the Calvin cycle, so the P is neither gained nor lost. Even with the leakage of 8%, if the algae is able to grow faster than the 8% loss, are we not taking additional P from the water to power the Calvin cycle in the new algae growth/cells and getting rid of P when we harvest?

Yes my analogies were a little misguided. As Garf pointed out, those studies compared algae Po excretion to bacterial biomass, NOT to algae biomass. But the revolving door analogy I think is still with merit. It is the quantity of P flux that is still a mystery. As Amphiprion just stated, that is something that may be insignificant in reality.

[Nick28]

If this were true, the lowest possible amount of P in a tank on average would continue to rise as years went by (creating a floor that rises) and you would have use another type of filtration or water change to bring it down.

organic p ends up as inorganic p at some point so it would have to show

I don't agree with it , but i'm willing to be proven wrong.

[xerophyte_nyc]

If this were true, the lowest possible amount of P in a tank on average would continue to rise as years went by (creating a floor that rises) and you would have use another type of filtration or water change to bring it down.

I don't quite understand what you're getting at.



organic p ends up as inorganic p at some point so it would have to show

Not necessarily, organic P can settle as detritus or become locked up in calcium.



I don't agree with it , but i'm willing to be proven wrong.

Instead of looking to be proven wrong, how about finding evidence that will prove you right? :)

[Nick28]

I don't quite understand what you're getting at.

If p became an issue it would show in the water column


Not necessarily, organic P can settle as detritus or become locked up in calcium.
detritus is food it does not stay detritus, old detritus totally changes form and new detritus gets created
Rock and sand will leach p untill exhaustion.


Instead of looking to be proven wrong, how about finding evidence that will prove you right? :)
I don't need too the burden of proof is on you making the claim against what works.

[xerophyte_nyc]

If p became an issue it would show in the water column

Do you mean with testing?



detritus is food it does not stay detritus, old detritus totally changes form and new detritus gets created

Well in the ocean, this is not the case. But in our aquariums, this could be more or less true.



Rock and sand will leach p untill exhaustion.

pH has to drop into the 7's for this to happen.



I don't need too the burden proof is on you making the claim against what works.

I'm not making any real claims. I'm not presenting any new facts. I'm just presenting some things that we know from research. I am not an author of any of the publications I linked. They already did the work. If there is some fact that is incorrect, it should be pointed out with whatever support there is against it.

The only thing in this entire discussion that could be considered original thought would be me questioning whether or not an ATS does not replace a skimmer. I presented some evidence supporting this, but there is no proof of anything.

[xerophyte_nyc]

In that same vein, there was a study I read a few months back that showed an increase in growth (at a reduced skeletal density, which decreases inversely with P concentration) with ever so slightly elevated P and that lack of growth is not a reasonable nor accurate sign of eutrophication/enrichment. If I can find it, that may be one blow against a portion of this argument.

Do you mean this?: phosphate-levels-increase-growth-rate-in-acropora-muricata (http://www.advancedaquarist.com/blog/increased-phosphate-levels-increase-growth-rate-in-acropora-muricata)

[Amphiprion]

Do you mean this?: phosphate-levels-increase-growth-rate-in-acropora-muricata (http://www.advancedaquarist.com/blog/increased-phosphate-levels-increase-growth-rate-in-acropora-muricata)

Yup, though I read the journal version. I don't mean for it to imply that phosphate is a good thing, only that basing a successful long term system or methodology on growth (or growth alone, really) may not be accurate--at least not in all circumstances. This goes back, again, to oversimplifying things. Can't say I'm not guilty of doing the same thing all the time, though. Everybody wants something they are supporting to work out eloquently and it doesn't usually happen that way.

[Nick28]

Do you mean with testing?

yes


Well in the ocean, this is not the case. But in our aquariums, this could be more or less true.

the ocean is the same scavengers of all sorts are not going to give up on the nutrients found in detritus.

39463947
http://www.absolutereef.com/forums/index.php?showtopic=15454


pH has to drop into the 7's for this to happen.

in localized areas it can but still as far as p binding and staying there, if coralline is growing on my rocks like crazy and P is known to inhibit calcification, how could this be true?

[xerophyte_nyc]

yes


All the hobbyist test kits only detect Pi, so we can't know how much Po there is. I wish there was a way to get this info, to me it is more valuable than knowing the Pi.



the ocean is the same scavengers of all sorts are not going to give up on the nutrients found in detritus.

Ocean is a special case. As detritus is processed on the seafloor, P becomes solubilized within the pore spaces in the sediment and then trapped in abyssal plains. After probably millions of years the P can be made available again through continental processes.

In a DSB, this soluble P makes its way down into anoxic zones. I guess the danger here is when the sand is disturbed, releasing all this P....or when the sand becomes saturated?



in localized areas it can but still as far as p binding and staying there, if coralline is growing on my rocks like crazy and P is known to inhibit calcification, how could this be true?

Pi inhibits coral skeletal formation. I don't know if coralline algae formation is the same, but if it is, that is a good point you make. I really don't know enough about coralline to offer any advice. Maybe encrusting algae have their own enzymes that can degrade or digest the rock they are attached to?

[Ace25]

... That being said, which would you rather do? Have a relatively trouble free tank for a long time, allowing nature to do its job or one that requires maintenance constantly? I've been down the latter path and I will never do it again, considering that missed maintenance one time could be absolutely crucial. As I said before, it is one of the most expensive, labor-intensive ways to go about doing this. We know that scrubbers can still grow corals (despite what was being said)--exactly how much "extra" growth is there to be gained from reef levels of phosphate? I'm not convinced it is terribly more significant and the tradeoffs, in my experience, are worse (i.e. starvation). If it really is that much more significant, I'd have to see it quantified to really lean in that direction. Of course, it would have to be appropriately quantified in an aquarium to begin making comparisons, since we'd need a baseline in our tanks to even start comparing to natural reefs. I think all of this would've fallen on deaf ears in the other thread, though.
I did the super expensive labor intensive method, had a great looking tank, but it was just way to much work and money. Now I do the 'let nature take care of things' method and I am having great success for mere pennies compared to what I used to dump into my other tank. I just tested my 60G, and it has had a pretty stable PO4 reading for the past 6 months, which today is .52. That is way higher than I would have ever run my tanks in the past, but you know what, I have SPS corals encrusting and growing up the back glass. The growth is actually better than what I get on my other tank, which usually hovers in the .09 area. After weighing how much time and money I was spending trying to control phosphates at a certain level and then seeing my other tank level off and find its own balance with no interaction I no longer consider phosphates themselves to really be an issue or something I should worry about and control as long as the tank can maintain a steady level on its own, it is the stability that is more important than the actual reading is most cases.

I think a better way to test a tank for phosphates is to test right before feeding, then 5 minutes after, then 1 hour after that to get a feel on how well the tank can control phosphates. If you feed and phosphates remain elevated for several hours then I would work on fixing that issue, feed less, possibly adding good bacteria, better designed scrubber, flow, etc.. there are many variables which could cause and resolve a particular issue.

[kotlec]

Good discussion . Adds value to this forum at my opinion. Doesnt matter where we end up, it gives wider view to things.

While analogy with rotating doors is nice, I feel its inaccurate at the same time. Algae is not the door it is array of doors. And there is basic difference. After screen cleaning we have lets say one rotating door. Next day we have 5 door and after week we have hundreds of rotating doors as algae continues to grow every day. Lets assume it is not full of passengers 100% , but we dont need that . When we clean screen we dump all doors together with their present passengers away and I would call this P and N export. If we keep algae and not harvest it - that would look like buffer. I see when people harvest their refugium and feed fish same algae . That happens in ocean. Animals eat algae but not export. All goes round. Algae is storage and conversion mechanism here.

There was information (or link to) on this site year or two ago how many P and N has dried harvested algae. Since we dump it away - we can say that scrubber cleans tank and not contaminates it with P. If this is enough ? - depends on tank and scrubber individually.

In our case secret is to have more rotating door at the end of week with more passenger inside. There goes your creativity and forum members experience how to make ATS more efficient.
My 0.02

[sabbath]

I find that there are many studies that conclude that skimmers are not very efective at removing organics. I have found them to say that it is in the 30-35% range. So as I read it, bubbles may not be the organics answer.

http://www.advancedaquarist.com/2010/1/aafeature

"It is apparent that the similarity in k values for the skimmed and the unskimmed tank trials do not support the notion that the skimmer is contributing in any material way to the removal of TOC from the reef tank water. That is, the natural TOC consumers (bacteria and other organisms) are completely adequate for returning the post-feeding TOC levels to approximately baseline values after ~ 24 hrs - the skimmer isn't required in this process. These observations therefore do not support the conventional wisdom that a skimmer is obligate for lowering and/or maintaining low TOC levels in a reef tank."

"Many factors contribute to the "value" of a skimmer to an aquarist, including quality of construction, size, footprint, noise level, ease of cleaning, energy efficiency of the pump, and of course, the ability to remove organic waste from aquarium water. Our data show that there are not compelling or remarkably large differences in measurable skimmer TOC removal metrics among the seven skimmers tested, although the Reef Octopus 150 consistently underperformed compared to the other skimmers. However, in the larger picture, it is equally apparent that if an aquarist runs a skimmer continuously (24/7), then any of the skimmers tested would perform adequately in terms of rate of TOC removal; the only practical differences might involve the frequency of skimmer cup cleaning. A perhaps more interesting observation to emerge from these skimmer studies involves not the rate of TOC removal, but rather the amount of TOC removed. None of the skimmers tested removed more than 35% of the extant TOC, leading to the conclusion that bubbles are really not a very effective medium for organic nutrient removal. If fact, the presence of refractory, or unskimmable, TOC, coupled with the likelihood that endogenous TOC consumers (bacteria, among others) also do not remove all of the TOC present (cf. Fig. 4), suggest that in an operational sense, TOC can be categorized as follows:"

[Ace25]

Look at the comments on that article, you will notice one thing that out performs what a skimmer does by a mile.. which is carbon. Skimmers remove 30-35% on average, Rox .08 carbon removes 85-90% of the same stuff. The only thing a skimmer does that carbon can't that adds a benefit to a tank is aeration but if your goal is to remove the stuff algae creates (oils, etc), carbon is the answer IMO. A small mesh bag of carbon in an overflow box for 1 weekend a month to me is equivalent to running a skimmer 24/7 for a month, but the skimmer in that time will also remove a lot of good stuff from the water that would have benefited the tank.


In some as yet unpublished work, we have shown that GAC is very effective at stripping aquarium water of its TOC load; from 60 - 90% removal, if I recall correctly, depending on specifics. We looked at ROX, HC2 and Black Diamond GAC's. The ROX was the winner by far.

[xerophyte_nyc]

I find that there are many studies that conclude that skimmers are not very efective at removing organics. I have found them to say that it is in the 30-35% range. So as I read it, bubbles may not be the organics answer.

http://www.advancedaquarist.com/2010/1/aafeature

Correct. TOC = Total Organic CARBON...I am more concerned about phosphorus than carbon. The same authors in the study you cited, followed up with a new article where they did an elemental analysis:

"Phosphorus analysis:
The 0.46% by weight of P present in the 5.18 gms of dry skimmate solid implies that there is 24 mgs of P present. Assuming all of the P is present as phosphate, PO43- (MW = 95, unknown counterion), then there are ~ 74 mgs (~ 1.4 %) of PO43- present in the 5.18 gm of dry skimmate solid. This amount equals ~ 14300 ppm of phosphate, which again is vastly more than the < 0.02 ppm of phosphate in the tank water."

Source: http://www.advancedaquarist.com/2010/2/aafeature

EDIT: And to further this, they calculated that during the week of skimmate collection, they added 42 mg of P from their food source. The skimmer pulled 24 mg. That is almost 60% of the input. I think that is very impressive. That would be the equivalent of doing a 60% water change every day, shortly after you feed.

I would expect that if someone were running a skimmer and an ATS, that the ATS would grow significantly more algae biomass if the skimmer were removed, if food input remains the same. The higher Po should feed more bacteria which would create more Pi for algae.

Does anyone here have experience with this?

[xerophyte_nyc]

Thank you for the reply. This is what I'm looking for. I want real world experiences, from someone who understands the processes and cycles going on.

I think that I represented certain facts pretty well, like the way in which algae cycle nutrients hand-in-hand with bacteria, and how phosphorus especially in its organic form is an important consideration for us aquarists. You can choose to "disagree" or not "believe" these things, but they are very real as demonstrated scientifically. Belief doesn't matter.

What I don't have enough knowledge of is how all this relates to real-life reefing. And that's the valuable info I want to gather for the benefit of everyone.


I did the super expensive labor intensive method, had a great looking tank, but it was just way to much work and money. Now I do the 'let nature take care of things' method and I am having great success for mere pennies compared to what I used to dump into my other tank. I just tested my 60G, and it has had a pretty stable PO4 reading for the past 6 months, which today is .52. That is way higher than I would have ever run my tanks in the past, but you know what, I have SPS corals encrusting and growing up the back glass. The growth is actually better than what I get on my other tank, which usually hovers in the .09 area. After weighing how much time and money I was spending trying to control phosphates at a certain level and then seeing my other tank level off and find its own balance with no interaction I no longer consider phosphates themselves to really be an issue or something I should worry about and control as long as the tank can maintain a steady level on its own, it is the stability that is more important than the actual reading is most cases.

I think a better way to test a tank for phosphates is to test right before feeding, then 5 minutes after, then 1 hour after that to get a feel on how well the tank can control phosphates. If you feed and phosphates remain elevated for several hours then I would work on fixing that issue, feed less, possibly adding good bacteria, better designed scrubber, flow, etc.. there are many variables which could cause and resolve a particular issue.

[Ace25]

Correct. TOC = Total Organic CARBON...I am more concerned about phosphorus than carbon. The same authors in the study you cited, followed up with a new article where they did an elemental analysis:

"Phosphorus analysis:
The 0.46% by weight of P present in the 5.18 gms of dry skimmate solid implies that there is 24 mgs of P present. Assuming all of the P is present as phosphate, PO43- (MW = 95, unknown counterion), then there are ~ 74 mgs (~ 1.4 %) of PO43- present in the 5.18 gm of dry skimmate solid. This amount equals ~ 14300 ppm of phosphate, which again is vastly more than the < 0.02 ppm of phosphate in the tank water."

Source: http://www.advancedaquarist.com/2010/2/aafeature

You are comparing the amount of phosphates that have been concentrated in a tiny amount of water (skimmer cup) vs phosphate levels in a large amount of water (overall tank volume), so of course phosphate levels will be much higher when in concentrated form. Those phosphates came out of the tank, that doesn't mean the tank has 14300 PPM of phosphates. By that line of thinking, if I just let the water evaporate in my tank, I am creating new salt out of thin air because my salinity goes up as water volume decreases, but we all know that isn't how it works. It is your math I have the biggest problem with, it doesn't make sense and seems to pull numbers out of thin air and then try and make those numbers correlate with something else as the above example proves.


An interesting and perhaps unanticipated observation is that only 34% of this solid skimmate material can be assigned to "organic carbon", TOC. Thus, 2/3 of the solid, water-insoluble part of the skimmate is not TOC, but rather inorganic material that may (or may not) have biogenic origins. If a substantial amount of this inorganic material does come from the shells of plankton, then it stands to reason that a large part of the detected organic material (TOC) probably constitutes the "guts" of these organisms.

The article is saying the stuff comes from food/microfauna, not from the water. We know skimmers remove food particles before they break down into N/P, and then they break down into N/P in a skimmer cup, which is also why you see much higher readings in skimmate vs a tank.

[xerophyte_nyc]

You are comparing the amount of phosphates that have been concentrated in a tiny amount of water (skimmer cup) vs phosphate levels in a large amount of water (overall tank volume), so of course phosphate levels will be much higher when in concentrated form. Those phosphates came out of the tank, that doesn't mean the tank has 14300 PPM of phosphates. By that line of thinking, if I just let the water evaporate in my tank, I am creating new salt out of thin air because my salinity goes up as water volume decreases, but we all know that isn't how it works. It is your math I have the biggest problem with, it doesn't make sense and seems to pull numbers out of thin air and then try and make those numbers correlate with something else as the above example proves.


The authors calculated that during the week of skimmate collection, they added 42 mg of P from their food source. The skimmer pulled 24 mg. That is almost 60% of the input. I think that is very impressive.

I did not do these experiments, so why do you suggest that I am the one pulling these numbers out of thin air?

EDIT: I just checked, turns out it is 42 mg added DAILY, not weekly, so the skimmer DID NOT pull out 60%. It pulled closer to a rate of 8% total.

If the skimmer is constantly pulling out Po at a rate of about 8%, that would be about the same thing as doing an 8% water change daily. Still not too bad.

[sabbath]

Well I'm not smart enough to get all this math thrown out here. But there are many tanks that get by with just running a ATS. So there must be something going on that the math does not see. For example Inland Aquatics has been running with scrubber only tanks for 20 some years.

" Inland Aquatics pioneered the use of Algal Turf Scrubbers for hobby and mariculuture applications in the early 90s. We took Dr. Walter Adey's prototypes, as used at the Smithsonian's Marine Systems Laboratory, and developed several ATScrubber (tm) and ecoTarium (tm) models. Since then we have used ATScrubbers exclusively on nearly all our marine systems, as well as many of our freshwater systems, for nearly 20 years. Until now, we have not marketed this amazing technology to anyone outside of our immediate area. Let's talk about the best kept secret in nutrient processing... ATS!"

[Ace25]

I have a real world example in my living room that this thread has yet to explain. If algae doesn't remove phosphates, then why does my 'ats only' tank have a stable phosphate reading for over a year now? It isn't an 'ideal' reading in my book, but it seems to work on that tank. I dump in A TON of food every day, much more than I should (6+ cubes for 6 fish), and still my phosphates remain stable. If algae doesn't remove phosphates, then what else would remove them on my tank because that is the only thing I do on it (clean the screen). No reactors, no skimmer, no water changes, just weekly cleaning of the screen. The tank is doing so well I had my clownfish lay another giant clutch of eggs last night.

This is where the math doesn't add up to me. I am dumping WAAAY more phosphates into my tank daily and if this thread was correct, I would have a constant steady rise in phosphates, but I don't. Why is that?

[sabbath]

I have a real world example in my living room that this thread has yet to explain. If algae doesn't remove phosphates, then why does my 'ats only' tank have a stable phosphate reading for over a year now? It isn't an 'ideal' reading in my book, but it seems to work on that tank. I dump in A TON of food every day, much more than I should (6+ cubes for 6 fish), and still my phosphates remain stable. If algae doesn't remove phosphates, then what else would remove them on my tank because that is the only thing I do on it (clean the screen). No reactors, no skimmer, no water changes, just weekly cleaning of the screen. The tank is doing so well I had my clownfish lay another giant clutch of eggs last night.

This is where the math doesn't add up to me. I am dumping WAAAY more phosphates into my tank daily and if this thread was correct, I would have a constant steady rise in phosphates, but I don't. Why is that?

I think that they will say it is because our test kits test for Pi and the ATS only removes Pi, right? But why if our Po is not being "removed?" That ATS only tanks have great long turn coral success? Something else must be consuming it. Bacteria?

[xerophyte_nyc]

Cool!


Well I'm not smart enough to get all this math thrown out here. But there are many tanks that get by with just running a ATS. So there must be something going on that the math does not see. For example Inland Aquatics has been running with scrubber only tanks for 20 some years.

" Inland Aquatics pioneered the use of Algal Turf Scrubbers for hobby and mariculuture applications in the early 90s. We took Dr. Walter Adey's prototypes, as used at the Smithsonian's Marine Systems Laboratory, and developed several ATScrubber (tm) and ecoTarium (tm) models. Since then we have used ATScrubbers exclusively on nearly all our marine systems, as well as many of our freshwater systems, for nearly 20 years. Until now, we have not marketed this amazing technology to anyone outside of our immediate area. Let's talk about the best kept secret in nutrient processing... ATS!"

[xerophyte_nyc]

I have a real world example in my living room that this thread has yet to explain. If algae doesn't remove phosphates, then why does my 'ats only' tank have a stable phosphate reading for over a year now? It isn't an 'ideal' reading in my book, but it seems to work on that tank. I dump in A TON of food every day, much more than I should (6+ cubes for 6 fish), and still my phosphates remain stable. If algae doesn't remove phosphates, then what else would remove them on my tank because that is the only thing I do on it (clean the screen). No reactors, no skimmer, no water changes, just weekly cleaning of the screen. The tank is doing so well I had my clownfish lay another giant clutch of eggs last night.


This is where the math doesn't add up to me. I am dumping WAAAY more phosphates into my tank daily and if this thread was correct, I would have a constant steady rise in phosphates, but I don't. Why is that?

Your testing kits only measure the Inorganic Pi, not the dissolved organic portion, or Po. Pi can be used so rapidly as soon as it is created that even a reading of 0 can be misguided. Po can only be measured using expensive lab technology, it is not something we as hobbyists have access to. Po by itself is not harmful to the tank inhabitants. Some of it is food for coral, some is food for algae, and some binds to sand and rock. Eventually, and keep in mind this eventuality could be many years there's just no way to know for sure, the sand becomes saturated. This situation leads to excess Po with nowhere for it to go because the sand is full. I guess at that point, more bacteria start to consume the Po and convert it to more and more Pi which can cause algae overgrowth or a bacterial bloom.

Someplace in your tank there is a very good sink for Po. Maybe it's your rock, maybe your sand, maybe there is detritus building up somewhere in your sump you are unaware of? The ATS itself also does a good job of collecting detritus, which goes in the garbage when algae is harvested. Nobody has discussed that really up until now but it might be something worth noting. Maybe an ATS's real benefit is in its ability to trap detritus?


One suggestion to remedy the problem of sand saturation is changing out portions of the substrate periodically. It's like replacing a bag of used GFO. Detritus contributes to the excess Po problem, so we need to clean up after our fish poop, so to speak. Water changes and skimmers remove some of the Po in the water column. We as hobbyists should not forget about the basics of aquarium husbandry. An ATS does not change that. That's the point of this thread. Not that an ATS is bad, but that we can't forget about the other stuff.

Basically, if a healthy tank all of a sudden shows uncontrollable algae growth, it is a sign that trouble is brewing. When you hear about "old tank syndrome" or tank crashes, some people think it is related to a build-up of Po after years of neglect or improper maintenance.

[xerophyte_nyc]

I think that they will say it is because our test kits test for Pi and the ATS only removes Pi, right? But why if our Po is not being "removed?" That ATS only tanks have great long turn coral success? Something else must be consuming it. Bacteria?

Just like anything else in this hobby, there will be success stories using every different method of filtration. There will also be failures. What we really need is documentation showing which methods are being used simultaneously, for ex scrubber + skimmer, scrubber +water changes, etc.

Nothing else is comsuming the Po. It binds to calcium. Matter doesn't disappear. Phosphorus is different from other nutrients. Nitrogen and carbon are gases, they can leave into the atmosphere. Phosphorus has to be physically removed. It sinks in water, so it accumulates as detritus in bacterial floc, and it binds to calcium in sand and rock.

[Ace25]

I also don't understand why you keep stating 'test kits don't test for organic phosphates'. That is another over generalization. Normal cheap test kits don't test for organic phosphates (like API), but the good ones that we use do test for organic phosphates.

http://www.lamotte.com/component/option,com_pages/mid,/page,60/#phosphate

[xerophyte_nyc]

I also don't understand why you keep stating 'test kits don't test for organic phosphates'. That is another over generalization. Normal cheap test kits don't test for organic phosphates (like API), but the good ones that we use do test for organic phosphates.

http://www.lamotte.com/component/option,com_pages/mid,/page,60/#phosphate

I don't think it's an over-generalization to state that most reefers do not test for organic phosphates. That issue can be settled easily with a simple poll. I doubt there are too many people who are doing so, I could be wrong.

[Amphiprion]

I don't use any higher end tests anymore. While it can be nice to get that narrower baseline, I don't find it necessary anymore nor worth the prices these kinds of tests command. It ties into my philosophy that anyone can have a successful tank, whether they've put hundreds or thousands of dollars into it (or inordinate amounts of time and effort... but I'm a bit lazy, admittedly).

[Garf]

I also don't understand why you keep stating 'test kits don't test for organic phosphates'. That is another over generalization. Normal cheap test kits don't test for organic phosphates (like API), but the good ones that we use do test for organic phosphates.

http://www.lamotte.com/component/option,com_pages/mid,/page,60/#phosphate

Ace from a quick look at that link, if the test kit turns blue to indicate phos, you need to add acid and nuke it for a while in the microwave, then neutralise with base and retest. Have you got a more detailed procedure as I am in a position to test this (if what I have described is correct).

[sabbath]

Does anyone have a list of kits that test for Po?
I have the Hanna checker Phosphorus test kit, does this one reading Po or Pi?
Thanks

[kaskiles]

Nice find Garf, here are the instructions:
http://www.lamotte.com/pages/common/pdf/instruct/7884.pdf

I think you can use this kit to digest (convert all phosphorous to orthophosphate) your tank water samples for measurement with any orthophosphate kit (hannah checker, etc.).
Before doing the total phosphorus in step C, might want to skip the water filtering step to include any suspended phosphorus.

So now with this auxiliary kit, anyone wanting to prove the theory in this thread has the tools to do so?

[Garf]

Excellent, I've got all that apart from the ammonium persulfate. Will see if I can get some when I get back to work. Thanks kaskiles

Presumably you could test algae concentration of P, using the same method!

Edit - Ammonium persulfate is on the bay at a few pounds for plenty

[xerophyte_nyc]

Presumably you could test algae concentration of P, using the same method!


You could test water incoming the scrubber, and outgoing for comparison. Also this should be tested during the ATS light cycle and day cycle separately.

And what I'm not sure of either is what is a normal Po level, and what is high? The discussion in this thread revolves around vague references to excess Po - but how much is excess? And remember the issue of the Po binding to calcium, how quick is that? I definitely think it best to test water in the sump where the ATS is located, preferably without any sand or rock to bind the Po.

[Garf]

Particularly interesting;

http://www.advancedaquarist.com/2010/10/aafeature

And for all those that think skimmers strip food, and only food from the water;

http://www.advancedaquarist.com/2010/2/aafeature/


The clincher, perhaps (in regard to the OP anyway);

http://i1269.photobucket.com/albums/jj597/Garf1971/f6316c445d9cafc2c275ba0d6f1d4082_zps21fd6935.jpg

[Ace25]

And for all those that think skimmers strip food, and only food from the water;

http://www.advancedaquarist.com/2010/2/aafeature/

I post that link so many times.. but I am confused by your statement as that article pretty much says most of the elements in the skimmer cup likely came from 'food', calcium/phosphorous came from microfauna shells and guts. They used carbon and GFO on the tank in the article, which removed most of the 'skimmable' oils, lipids, etc, and the GFO removed the inorganic phosphates.

Typical daily feedings included one cube of Hikari mysis shrimp, one cube of PE mysis shrimp, a pinch of flake food, and a pinch of pellet food. Thrice weekly, the Reef Nutrition products Phytofeast, Rotifeast, Oysterfeast and Arctipods were used, and a sheet of nori was added once per week. The skimmer cup was cleaned weekly, and Granular Activated Carbon (GAC), Granular Ferric Oxide (GFO), a calcium reactor, and a UV sterilizer all were used continuously.


Therefore, a total ~ 95% of the dry water-insoluble skimmate is accounted for! What are the sources of these chemical compounds in the skimmate? The biogenic opal is likely from the shells of diatoms, small members of the phytoplankton family of marine microbes. The CaCO3 (and MgCO3) might have both biogenic and abiological sources. A calcium reactor was operating throughout the experimental skimmate collection period, and so some of the CaCO3 might just be microparticulates emitted from this device. Alternatively, the CaCO3 might arise from the shells of planktonic microbes from the coccolithophore (Mitchell-Innes, 1987; Stanley, 2005) and foraminifera families. These plankton components are prevalent under certain conditions in seawater, but there presence in aquarium water has not been established. It is not possible to distinguish between these biological and abiological sources of CaCO3 at present. Future experiments in which skimmate is collected without a running calcium reactor might shed some light on this point. The phosphate present in the skimmate could not come from inorganic phosphate in the water column; that ion would have been removed by the thorough washing with water. It is possible that some of this phosphate is in the form of insoluble calcium phosphate, but that occurrence would be unlikely as Ca3(PO4)2 is formed at rather high pH, which is not characteristic of the skimmate liquid (pH = 7.67, see below). By default, then, it is most likely derived from organic phosphate; that is, many biochemicals within diatoms and all other living organisms (coccolithophores, foraminifera, bacteria, humans, etc) have attached phosphate groups. Aquarium organisms recruit these phosphate molecules from the inorganic phosphate in the water column and then attach them to the organic biochemicals. Thus, they effectively concentrate phosphate from the water, and that phosphate is then removed (within the intact organism) upon skimming. From this perspective, skimming does contribute to the removal of inorganic phosphate from aquarium water.

An interesting and perhaps unanticipated observation is that only 34% of this solid skimmate material can be assigned to "organic carbon", TOC. Thus, 2/3 of the solid, water-insoluble part of the skimmate is not TOC, but rather inorganic material that may (or may not) have biogenic origins. If a substantial amount of this inorganic material does come from the shells of plankton, then it stands to reason that a large part of the detected organic material (TOC) probably constitutes the "guts" of these organisms. Thus, perhaps not that much of the TOC removed by skimming is actually free-floating organic molecules. One caveat on this interpretation, of course, is the fact that ~ 90% of the crude original skimmate was washed away with water. Perhaps that water-soluble fraction contained significant quantities of dissolved organic carbon, which would be undetected by the above analysis.

[Garf]

8% inorganic ions
26 % of CaCO3
7% of MgCO3
21% of biogenic opal (SiO2)
38% of organic material
1.5% of phosphate
1.3 % of ferric oxide
These materials sum up to ~ 103%, which is pretty close to the theoretical maximum of 100%. Any discrepancies can be easily explained by the numerical uncertainty introduced through all of the assumptions. That is, even with all of the assumptions and approximations cited in this analysis, the sum total of the mass works out to within 3% of "perfect". Once again, the organic material removed in the skimmate solid is a minor component, although at an average of 38% (C vs. N vs. H analysis), it is a little higher than the 34% value derived from the heavily washed skimmate solid sample and much higher that the amount of DOC in the liquid fraction (~ 10%). In total, the 8.49 gm of total solids removed during the week of skimming contain approximately 318 mg of water-soluble organics (~ 4%) and approximately 2.12 gms of water-insoluble organics (~ 25%). Thus, by a large margin, the bulk of the organics removed by skimming are not DOC (dissolved organic carbon). The inorganic compounds CaCO3 and SiO2 constitute the majority of the skimmate solid mass, much as they did in the heavily washed skimmate sample analyzed first. As discussed in that analysis, the source of these compounds is not assignable from these data, but a biological source for the SiO2 (biogenic opal), diatom shells, is likely. The CaCO3 might arise from both inorganic sources (i.e., calcium reactor CaCO3 particle ejection) and organic sources (the shells of foraminifera and/or coccolithophores).
One of the surprising observations to emerge from the original skimmer performance studies is that only approximately 20 - 35% of the measurable TOC in aquarium water is removed by skimming. That observation might now seem a little less surprising when viewed in the context of the skimmate component analysis. Thus, only ~ 29 % (25% from the solid + 4% from the liquid) of the skimmate removed by the H&S 200 skimmer from authentic reef tank water over the course of a week can be assigned to organic material. So, skimming does not remove all that much of the TOC present in aquarium water, and the skimmate does not contain all that much TOC.

ConclusionsThe chemical/elemental composition of skimmate generated by an H&S 200-1260 (tel:200-1260) skimmer on a 175-gallon reef tank over the course of several days or a week had some surprises. Only a minor amount of the skimmate (solid + liquid) could be attributed to organic carbon (TOC); about 29%, and most of that material was not water soluble, i.e., was not dissolved organic carbon. The majority of the recovered skimmate solid, apart from the commons ions of seawater, was CaCO3, MgCO3, and SiO2 - inorganic compounds! The origin of these species is not known with certainity, but a good case can be made that the SiO2 stems from the shells of diatoms. The CaCO3 might be derived from other planktonic microbes bearing calcium carbonate shells, or might come from calcium reactor effluent. To the extent that the solid skimmate consists of microflora, then some proportion of the insoluble organic material removed by skimming would then simply be the organic components (the "guts") of these microflora. These microflora do concentrate P, N, and C nutrients from the water column, and so their removal via skimming does constitute a means of nutrient export.

[Ace25]

I am very confused as to what you are trying to say/point out with that article? I think we are reading the same thing and somehow coming to 2 different conclusions. Everything I read in that article screams 'food' is the source of the elements in a skimmer cup, not all of it is food we dump in, but also food that grows in the tank (copepods, foraminifera, etc.). The reason I think 'food' is the main source is because they did use GFO and Carbon on the tank, and we know carbon can remove more stuff than a skimmer (except large things), and GFO will remove inorganic phosphates, which just leaves organics and inorganics bound to living things that get pulled into the cup and decompose.

[Garf]

Sorry, just pointing out that skimming does not just remove food, anymore than harvesting half a kilo of algae a week. The anti skimming standpoint (not from you btw) is akin to the anti scrubbing view. Most of the available food (DOCs) has been consumed before it gets skimmed out, hence exported through a different mechanism.

[Ace25]

ok, now I understand where you are coming from. Thanks for the clarification.

I think the conclusion is the title of this thread is false, algae does export phosphates. What is still a mystery is what processes are at play that make that happen, and what percentage those processes aid in phosphate removal.

As an example with completely made up numbers, 50% of to total phosphates within exported algae are taken in directly via the algae for growth, 40% comes from a symbiotic relationship with proper bacteria strains, and the remaining 10% comes from the filtering effect of the algae catching detritus. In that made up scenario it may be possible to not have the correct bacteria symbiosis which in turn could make the scrubber 40% less efficient.

[Amphiprion]

Nor are abiotic factors taken into consideration, such as localized high pH, which would promote phosphate precipitation. The precipitates cling to the algae to an extent, thus allowing even more export. I haven't seen in situ studies or observations confirming this, but it is an effect that Adey originally proposed could technically occur in and around the turf. Something else to think about, anyway.

[Garf]

Nor are abiotic factors taken into consideration, such as localized high pH, which would promote phosphate precipitation. The precipitates cling to the algae to an extent, thus allowing even more export. I haven't seen in situ studies or observations confirming this, but it is an effect that Adey originally proposed could technically occur in and around the turf. Something else to think about, anyway.

Well, that makes sense. It also throws up another conundrum. From a bit of research I did on blue light and algae, it appeared (to me anyway) that blue light induced an acid production response, to release co2 from carbonate it was assumed. Would this also release any phosphate bound up in the precipitate, therefore reducing the total amount of phos harvested from a screen. Ie red lights only could increase the total phos removed whist harvesting?

[xerophyte_nyc]

"Algal growth, ordinarily phosphorus limited, depends inversely on bacterial phosphorus utilization and growth. We envision phytoplankton and bacterioplankton dynamics as being tightly coupled: both should respond in a similar fashion to trophic variations and in an inverse manner to allochthonous carbon supplies. Although this scheme will undoubtedly prove to be oversimplified (see Cole 1982), we consider it to be a workable starting point for predicting algal and bacterial interactions in situ."


Nice study discussing the tightly-coupled phosphorus sharing between bacteria and algae. They rely on each other. They can be considered as indicators of trophic level. Lots of phosphate = lots of bacteria = lots of algae. As long as algae is present, phosphates are high. ATS = high phosphates. It can't be any other way. If ATS was exporting phosphates then it wouldn't support itself. Catch 22. Unless you see the algae growth on an ATS getting weaker and less on a week to week basis, how could it be exporting phosphate?

A comparison of the abilities of freshwater algae and bacteria to acquire and retain phosphorus (http://nospam.aslo.org/lo/toc/vol_29/issue_2/0298.pdf)

[xerophyte_nyc]

Nor are abiotic factors taken into consideration, such as localized high pH, which would promote phosphate precipitation. The precipitates cling to the algae to an extent, thus allowing even more export. I haven't seen in situ studies or observations confirming this, but it is an effect that Adey originally proposed could technically occur in and around the turf. Something else to think about, anyway.

Also I have seen it mentioned that the ATS is very good at physically trapping detritus. But this potential trapping, and phosphate clinging, are somewhat negated by the fact these particles are sitting there and decomposing before being physically removed.

I think that cleaning the turf screen more regularly could lead to a significant improvement in results. You are removing trapped detritus more often before it deteriorates, and you are removing algae at a time further from when it starts to decay and release more Po into the water. There is also the aspect of removing bacterial biomass which grows together with algae on the screen. I know its more work but it would seem twice weekly screen cleaning could be better than weekly.

[xerophyte_nyc]

Well, that makes sense. It also throws up another conundrum. From a bit of research I did on blue light and algae, it appeared (to me anyway) that blue light induced an acid production response, to release co2 from carbonate it was assumed. Would this also release any phosphate bound up in the precipitate, therefore reducing the total amount of phos harvested from a screen. Ie red lights only could increase the total phos removed whist harvesting?

I think on a screen it wouldn't matter because there is no calcium source on it. I think the breakdown of calcium-phosphate bonds happens in proximity of the acid source. This would impact algae growing on live rock. Another example of how algae and bacteria work hand in hand. Algae helps bacteria nearby by making acid to liberate more Po, which the bacteria use to give the algae more Pi.

[Bilk]

Scrubbers are utilized on a large scale in the Everglades and in other coastal marsh areas to control and remove phosphorus runoff from farming. I think if anyone wants to really understand how these work and what processes are taking place, they should contact Ecological Systems or some other entity. I'm sure they would be willing to share their data or explain the process. I don't have that level of understanding of biology or chemistry so I'll leave this to others. However I think there's a lot of bad science being tossed about here. Not an attack on anyone. Just an observation. Taking bits of information from various sources and trying to piece them together isn't very scientific. As I said, turf scrubbers wouldn't be utilized on a commercial level for water purification and land management, if they weren't effective or if they were contributing more to the problem of managing phosphorus runoff. JMO of course :)

[Ace25]

One more variable I have always wondered about.. the screen material itself. It is plastic.. bacteria eats plastics.. so does the screen act as sort of a 'bio pellet'? I believe so. Run a screen for over 12 months and see how brittle the screens become. Yes, plastics will become brittle over time but that is normally caused by UV deteriorating the plastic, which I don't have in my ATS environments. As soft as the plastic is on the screen and how quickly it seems to become brittle I do think bacteria is consuming some of it for the carbon source. On my systems any screen over 12 months old (which is the recommended replacement time for a screen anyway) I can clean the algae off and then if I wanted I could crumble the screen into tiny bits and pieces in my hand due to how brittle it is.

[sabbath]

Well I'm used to watching coral reactions to changes that I make. As I just switched from running the Full Zeovit system 3 Months ago. I can tell when things are off and when I need to add aminos or strip the nutrients more. It usually takes a few days to a week to see after making a change.
While on my last couple of months on zeo I stopped all of the algae control methods. Because I wanted to try a ATS and have it deal with the algae part. Long story short, It did not work for me to run zeo with a ATS. So there is a good question for you. Why didn't it work? Anyway I stopped zeo and could not fathom not running a skimmer. As I have had one on my old 125g reef from the early 80's.

So I went;
Skimmer
ATS
Rox 8 Carbon in a reactor(1/2 cup in a 140g system)

This was too much striping of the water. I was starting to lose LPS corals. I pulled the Skimmer (uff) and the coral decline stopped. I ran this way for about a month and all was good with the corals and their colors. The algae is still on a slow decline. I now run the same amount of carbon in a filter bag passively( in a baffle) in the sump. All is still looking good at this point. Corals still not coming back from the over stripping. So I just started today to add a little amino's and see how things react.

So for now this is what is keeping things going in the right direction for me;
ATS
No Skimmer
Rox 8 (1/2 cup passive)
Light Amino dosing
10% month WC

So may I ask how is possible to run a skimmer with a scrubber? I would not have any LPS and not sure about the SPS. Because I stopped before it may have hurt them.

[xerophyte_nyc]

Scrubbers are utilized on a large scale in the Everglades and in other coastal marsh areas to control and remove phosphorus runoff from farming. I think if anyone wants to really understand how these work and what processes are taking place, they should contact Ecological Systems or some other entity. I'm sure they would be willing to share their data or explain the process. I don't have that level of understanding of biology or chemistry so I'll leave this to others. However I think there's a lot of bad science being tossed about here. Not an attack on anyone. Just an observation. Taking bits of information from various sources and trying to piece them together isn't very scientific. As I said, turf scrubbers wouldn't be utilized on a commercial level for water purification and land management, if they weren't effective or if they were contributing more to the problem of managing phosphorus runoff. JMO of course :)

Waste management: big difference I think...do they recirculate the effluent back to the the source of the runoff? I don't think they do. That would set up a super microbial-algal loop. That is the problem with aquarium ATS, water goes back into the tank to recirculate. And here are a couple references that review P removal/ waste management. Another commercial application of ATS is biofuels - there are other monetary benefits to ATS in waste management, its not just P.

ATS success may have more to do with the screen and algal mat trapping detritus and the associated biofilm for eventual export, than its inherent ability to use phosphorus. Just theorizing here.

Understandably some people here are questioning the research being presented. I still have not seen anyone counter with some research to dispute that algal utilization of P may not be that efficient P export. I'm not saying that the science is unequivocal, because obviously marine studies and petri dishes cannot translate directly to an aquarium, but the concepts are there for interpretation. I did not do these experiments. Don't shoot the messenger.

http://www.sciencedirect.com/science/article/pii/S0925857404000795
http://hydromentia.com/Products-Services/Algal-Turf-Scrubber/Product-Documentation/Assets/2002-Algae-NP-Removal.pdf

[Ace25]

Waste management: big difference I think...do they recirculate the effluent back to the the source of the runoff? I don't think they do. That would set up a super microbial-algal loop. That is the problem with aquarium ATS, water goes back into the tank to recirculate. And here are a couple references that review P removal/ waste management. Another commercial application of ATS is biofuels - there are other monetary benefits to ATS in waste management, its not just P.

ATS success may have more to do with the screen and algal mat trapping detritus and the associated biofilm for eventual export, than its inherent ability to use phosphorus. Just theorizing here.

Understandably some people here are questioning the research being presented. I still have not seen anyone counter with some research to dispute that algal utilization of P may not be that efficient P export. I'm not saying that the science is unequivocal, because obviously marine studies and petri dishes cannot translate directly to an aquarium, but the concepts are there for interpretation. I did not do these experiments. Don't shoot the messenger.

http://www.sciencedirect.com/science/article/pii/S0925857404000795
http://hydromentia.com/Products-Services/Algal-Turf-Scrubber/Product-Documentation/Assets/2002-Algae-NP-Removal.pdf

First, http://lmgtfy.com/?q=algae+phosphorus+uptake

Quote from one of the first links:

Bacterial uptake of inorganic phosphate (closely investigated in Escherichia coli) is maintained by two different uptake systems. One (Pst system) is Pi-repressible and used in situations of phosphorus deficiency. The other system (Pit system) is constitutive. The Pit system also takes part in the phosphate exchange process where orthophosphate is continuously exchanged between the cell and the surrounding medium.
Algal uptake mechanisms are less known. The uptake capacity increases during starvation but no clearly defined transport systems have been described. Uptake capacity seems to be regulated by internal phosphorus pools, e.g., polyphosphates. In mixed algal and bacterial populations, bacteria generally seem to be more efficient in utilizing low phosphate concentrations. The second half of this paper discusses how bacteria and algae can share limiting amounts of phosphate provided that the bacteria have pronouncedly higher affinity for phosphate. Part of the solution to this problem may be that bacteria are energy-limited rather than phosphate-limited and dependent on algal organic exudates for their energy supply.
The possible phosphate exchange mechanism so convincingly demonstrated in Escherichia coli is here suggested to play a key role for the flux of phosphorus between bacteria and algae. Such a mechanism can also be used to explain the rapid phosphate exchange between the particulate and the dissolved phase which always occurs in short-term 32P-uptake experiments in lake waters.

Second, Bio-Fuels do not use ATS type of technology, they use micro algae, not macro, and use closed loop bio reactors to grow the algae.

Third, waste treatment plants use bio-pellets (it is where they were developed before the aquarium hobby started using them). not algae to filter waste water.

Fourth, for 'natural filtration of run off' they use Mangroves, but it takes many MILLIONS to have any real effect. They chose those plants due to how easy they are to plant (put them in a pod and drop them out of a plane/helicopter to cover acres at a time). If there was another plant that was as hardy as a mangrove that could be mass planted and had better N/P/K uptake ratios I am sure we would use them. I don't know anywhere that uses 'hair algae' or 'turf algae' to clean water on a large scale other than nature.

[Bilk]

Some easy Google searches will provide information that supports the idea that algal turf scrubbers are indeed utilized for waste management and control of runoff from farming operations. It's really not disputable. Bio pellets are also used as are other forms of water purification. I'm not even sure why this idea is debated. I just plucked some at random. I'm sure there is much more to be found on the subject.

http://www.algalturfscrubber.com
http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?cmd=prlinks&dbfrom=pubmed&retmode=ref&id=11804130
http://www.ars.usda.gov/is/AR/archive/may10/algae0510.htm?pf=1

[Bilk]

If someone is inclined, or just happens to have a subscription :), they could dissect this paper (http://www.iwaponline.com/wst/03307/wst033070191.htm). I would have no clue as to the specifics of the science. As a matter of fact, that site probably has all the data and info anyone could ever want about the subject.

[Bilk]

Waste management: big difference I think...do they recirculate the effluent back to the the source of the runoff? I don't think they do. That would set up a super microbial-algal loop. That is the problem with aquarium ATS, water goes back into the tank to recirculate. And here are a couple references that review P removal/ waste management. Another commercial application of ATS is biofuels - there are other monetary benefits to ATS in waste management, its not just P.

ATS success may have more to do with the screen and algal mat trapping detritus and the associated biofilm for eventual export, than its inherent ability to use phosphorus. Just theorizing here.

Understandably some people here are questioning the research being presented. I still have not seen anyone counter with some research to dispute that algal utilization of P may not be that efficient P export. I'm not saying that the science is unequivocal, because obviously marine studies and petri dishes cannot translate directly to an aquarium, but the concepts are there for interpretation. I did not do these experiments. Don't shoot the messenger.

http://www.sciencedirect.com/science/article/pii/S0925857404000795
http://hydromentia.com/Products-Services/Algal-Turf-Scrubber/Product-Documentation/Assets/2002-Algae-NP-Removal.pdf
So you posted some links, but what do they say? What were the conclusions? Do they support your hypothesis that ATS doesn't effectively bind and remove PO? I wouldn't know what I was looking at and one link requires a subscription.

[xerophyte_nyc]

So you posted some links, but what do they say? What were the conclusions? Do they support your hypothesis that ATS doesn't effectively bind and remove PO? I wouldn't know what I was looking at and one link requires a subscription.

The first link is an abstract only, but it demonstrates that eutrophic algae exist right at inflow, replaced by oligotrophic species downstream. Nothing surprising. This shows how the type of algae present is indicative of nutrient levels. If an ATS was effectively sucking out P and lowering nutrient levels in a tank, then the turf itself should also change in quality and quantity of algae, over time.

Second link: "nutrient removal by algal turfs is a combination of uptake by the turf’s microbial flora and fauna as well as by nonspecific adsorption and physical trapping of organic particles. At present, we cannot differentiate between these processes." Based on this info, maybe the ATS really is just a detritus and bacterial trap.

[Garf]

If someone is inclined, or just happens to have a subscription :), they could dissect this paper (http://www.iwaponline.com/wst/03307/wst033070191.htm). I would have no clue as to the specifics of the science. As a matter of fact, that site probably has all the data and info anyone could ever want about the subject.

I like the sound of this bit;

This indicated that pH mediated precipitation probably accounts for much of the phosphorus removal by the ATS and for the high mean phosphorus content of the harvested solids

I have deliberately aerated my screen to prevent high screen pH (and increase Co2 availability). My nitrate and phosphate indicates a steady state, with it in balance. Perhaps if I stop this and increase my screen pH I could show an increased phos removal effect. I could also add Kalk to the sump to aid this effect. I'm always game for a bit of experimenting.

[Bilk]

I can only comment on the second link, as I don't have a subscription to the first. That study was conducted 11 years ago. Maybe someone somewhere has newer information providing a better understanding of what is happening? The experiment was conducted in 2002. Did they do anything subsequent to this?

I think a simple experiment that can be done in the aquarium is to use filter socks before the scrubber to see if growth is inhibited by not receiving the detrital material you believe is feeding the algae. Mine isn't running so I cannot be the guinea pig :) I guess that would take some modification on someone's part as well.

[xerophyte_nyc]

Here is another Adey article, from 2011. I have access to most journals via my NYU proxy.:

Algal Turf Scrubbing: Cleaning Surface Waters with Solar Energy while Producing a Biofuel
Adey, Walter H; Kangas, Patrick C; Mulbry, Walter. Bioscience61. 6 (Jun 2011): 434-441.
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As human populations have expanded, Earth's atmosphere and natural waters have become dumps for agricultural and industrial wastes. Remediation methods of the last half century have been largely unsuccessful. In many US watersheds, surface waters are eutrophic, and coastal water bodies, such as the Chesapeake Bay and the Gulf of Mexico, have become increasingly hypoxic. The algal turf scrubber (ATS) is an engineered system for flowing pulsed wastewaters over sloping surfaces with attached, naturally seeded filamentous algae. This treatment has been demonstrated for tertiary sewage, farm wastes, streams, and large aquaculture systems; rates as large as 40 million to 80 million liters per day (lpd) are routine. Whole-river-cleaning systems of 12 billion lpd are in development. The algal biomass, produced at rates 5 to 10 times those of other types of land-based agriculture, can be fermented, and significant research and development efforts to produce ethanol, butanol, and methane are under way. Unlike with algal photobioreactor systems, the cost of producing biofuels from the cleaning of wastewaters by ATS can be quite low. [PUBLICATION ABSTRACT]

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As human populations have expanded, Earth's atmosphere and natural waters have become dumps for agricultural and industrial wastes. Remediation methods of the last half century have been largely unsuccessful. In many US watersheds, surface waters are eutrophic, and coastal water bodies, such as the Chesapeake Bay and the Gulf of Mexico, have become increasingly hypoxic. The algal turf scrubber (ATS) is an engineered system for flowing pulsed wastewaters over sloping surfaces with attached, naturally seeded filamentous algae. This treatment has been demonstrated for tertiary sewage, farm wastes, streams, and large aquaculture systems; rates as large as 40 million to 80 million liters per day (lpd) are routine. Whole-river-cleaning systems of 12 billion lpd are in development. The algal biomass, produced at rates 5 to 10 times those of other types of land-based agriculture, can be fermented, and significant research and development efforts to produce ethanol, butanol, and methane are under way. Unlike with algal photobioreactor systems, the cost of producing biofuels from the cleaning of wastewaters by ATS can be quite low.

Keywords: algae, biofuel, ecological engineering, nitrogen, phosphorus

There is a growing need for low-cost technologies to improve water quality in degraded aquatic ecosystems. Ecological engineering offers an approach to managing this problem through the development of controlled ecosystems designed specifically for water treatment (Mitsch and Jørgensen 1989, 2004, Kangas 2004). Ecologically engineered systems use the free energies from nature as a subsidy, along with some inputs from human technology, to provide less costly solutions to certain environmental problems than conventional designs powered by fossil fuel-based energies. Free energies include the "natural machineries" that are the products of evolution, along with natural energy inputs of sunlight, wind, and rain. Well-known examples of ecologically engineered systems are treatment wetlands (Kadlec and Knight 1996) and bioengineered vegetation used for erosion control (Schiechtl and Stern 1997). The main trade-off in these systems is that they require large areas of land for implementation because they are driven by solar energy. Therefore, these systems are effective alternatives in rural settings where land is available, but they are less applicable in urban settings where land costs are high. In this article, we describe an ecologically engineered, algae-based system (the algal turf scrubber, or ATS(TM)).

In recent years, great attention has been devoted to the use of algae to produce biofuels (Chisti 2007); it has been known for many decades that nutraceutical production can be of great value (Constantine 1978, Lembi and Waaland 1988, Radmer 1996). However, aquatic algae have greater photosynthetic potential than higher-trophic-level plants, and algae are also capable of using solar energy to facilitate nutrient removal (of nitrogen [N], phosphorus [P], carbon dioxide) and injecting oxygen into degraded waters (Beneman and Oswald 1996). The greatest opportunities for algal cultures lie in combined wastewater cleanup and biofuel and nutraceutical production. In this article, we introduce the ATS process, which has been researched and developed for many years, scaled up to multiacre levels, and is now ready for use at the watershed scale.

ATS: A biomimicry of coral reef primary production

Since the studies of Odum and Odum (1955) at Enewetak Atoll, it has been thought that tropical coral reefs in lownutrient seas could actually be highly productive. Odum and Odum suggested that small attached and boring algae were the principal source of this productivity. Following an extensive yearlong analysis of coral reefs on St. Croix in the Caribbean in the late 1970s, Adey and Steneck (1985) demonstrated that primary productivity values 5 to 10 times higher than those of terrestrial forests and agriculture were routine and were limited primarily by the amount of available light. The primary source of the productivity-driving photosynthesis was the dense, biodiverse turf of filamentous algae that covered roughly 40% of the reefs' carbonate surfaces. Experimental screens established at many reef sites across the eastern Caribbean demonstrated mean algal turf productivities of 5 to 20 grams (g) per square meter (m2) per day (all productivity values reported in this article reflect dry weight; figure 1; Adey 1987). The researchers involved in this fieldwork showed that the oscillating motion (surge) created by trade-wind wave action was a principal factor driving high productivity (Carpenter et al. 1991, Adey and Loveland 2007).

During the 1980s and 1990s, the principal elements of this algal-turf-driven, high coral-reef primary productivity were ecologically engineered to create a device called an ATS (Adey 1983; see also the parallel work by Sladeckova et al. 1983 and Vymazal 1989). Integrating water flow and surge with high light intensity and frequent harvest, ATS units achieved high levels of primary productivity and were used to control water quality in a considerable variety of enclosed microcosms and mesocosms of coral reefs, estuaries, and rocky shores (reviewed by Adey and Loveland 2007). Early work on ATS involved designing pulsing hydraulic systems to mimic the wave energy found in coastal systems. However, because freshwater attached algae behave similarly to marine algal systems (Mulholland et al. 1994, 1995), freshwater ATS were also developed (Adey and Loveland 2007). The original wild ecosystems (coral reefs) that ATS "mimicked" were very-low-nutrient, light-limited systems. However, later in the 1980s, small ATS units were employed on high-nutrient source waters of raw sewage and chicken manure, and they were both quite successful at removing N, P, and biological oxygen demand (Adey and Loveland 2007) and produced even higher levels of harvest production. Beginning in the early 1990s, a scaling-up process of ATS units was initiated for both large-scale finfish aquaculture and wastewater treatment. One of the authors (WHA) (eventually) obtained a series of six patents that would potentially bring venture capital into the scaling-up process (US patents 4,333,263; 4,966,096; 5,097,795; 5,715,774; 5,778,823; and 5,851,398). Landscape-scale ATS systems have been built as large as 3 hectares (ha) in dimension and as great as 150 million liters per day (lpd) in capacity; a set of ATS units for whole-river amelioration of 11 billion lpd is now in final engineering design.

The ATS system consists of an attached algal community, which takes the form of a "turf," growing on screens in a shallow trough or basin (referred to as a raceway) through which water is pumped. The algal community provides water treatment by the uptake of inorganic compounds and release of dissolved oxygen through photosynthesis. Water is pumped from a body of water onto the raceway, and algae remove the nutrients through biological uptake and produce oxygen as the water flows down the raceway. At the end of the raceway, water is released back into the water body, with a lower nutrient concentration and a higher dissolved oxygen concentration than when it was pumped onto the raceway. The nutrients that have been removed, or "scrubbed," from the water body are stored in the biomass of the algae growing on the screen. The algae are harvested approximately once per week during the growing season, thus removing nutrients from the waterway in the algal biomass. Harvesting is important because it rejuvenates the community and leads to higher growth rates; harvesting also prevents or reduces the potential effects of invertebrate micrograzers. In fact, biomass production rates of ATS are among the highest of any recorded values for natural or managed ecosystems (Adey and Loveland 2007). Because of the fast growth rate of algae on ATS, this technology can remove nutrients and produce oxygen at a high rate. Design features of ATS include the flow rate of water, the slope of the raceway, the loading rate of nutrients in the water, and the type of screen used to grow algae.

Landscape-scale ATS systems

The scale-up of ATS systems for sewage treatment began in the mid 1990s with a tertiary wastewater unit in Patterson, California (Craggs et al. 1996). The algae-growing surface in this case was an inclined, textured surface of high-density polyethylene (a soil-bed liner) 150 m long and 7 m wide (figure 2). Secondary wastewater from the city's sewage plant flowed over this surface in a series of pulses, with flows varying between 445,000 and 890,000 lpd. A wide variety of chemical, physical, and biotic operational parameters were analyzed, and the algal biomass was mechanically vacuum harvested at one- to two-week intervals, depending on the season. Harvest production (including trapped organic particulates) in June and July typically ranged from 50 to 60 g per m2 per day. In December and January, because of the extremely foggy conditions of the Central Valley, algal productivity was 8 to 12 g per m2 per day. The yearly mean of algal production was 35 g per m2 per day. The ash-free dry weights were 40% to 50% of the total dry weight.

From the percentage of nutrients in the harvested solids (3.1% N and 2.1% P) and the yearly mean productivity of 35 g per m2 per day, the yearly mean removal rates of N and P in the Patterson pilot plant were determined to be 1.1 ± 0.5 and 0.7 ± 0.2 g per m2 per day, respectively. The yearly mean concentration of nutrients in the incoming wastewater was 5 milligrams (mg) per liter (L) total N and 3 mg per L total P. Higher concentrations of nutrients in influent water can lead to even higher removal rates. Mean removal rates of more than 4 g N per m2 per day were achieved on a stream-treatment ATS in Arkansas; this unit was placed several hundred meters downstream from a municipal treatment plant outlet (Adey 2010).

On sunny days, the pH of the ATS effluent at Patterson reached 10 or higher; at pH values of 8.0 to 10, much of the P in the water column was precipitated as calcium hydroxyapatite into the algal mat. Not all dissolved P is removed from the water column because of partial resolution at lower nighttime pH values. Precipitation into the algal biomass of numerous divalent and trivalent cations (Ca+, Mg+, Al+, Fe+, etc.) also occurs with phosphates, and probably with carbonates as anions. The system thus acted as a partial deionizer as well as a nutrient sink.

Non-point-source nutrient removal

In 1991, a pilot-scale ATS floway (15 m long, 0.75 m wide; Adey et al. 1993) was tested for six months on a sugar farm in the Florida Everglades. The algae self-seeded from the source drainage canal and included species of the genera Cladophora, Spirogyra, Enteromorpha, and Stigeoclonium, as well as a variety of filamentous diatoms such as Eunotia and Melosira (figure 3). A weekly harvest interval of the algal biomass and vacuum harvesting with a standard shop wet-vacuum was employed. The source water in this experiment had total P concentrations of 0.04 to 0.05 mg per L. Mean dry algal production levels ranged from 33 to 39 g per m2 per day, with lower rates occurring in the winter and higher rates in the late spring. The mean P content of harvested biomass ranged from 0.3% to 0.4%. During the spring (a period of average solar intensity and low nutrient supply), the calculated total P removal rate ranged from 0.1 to 0.14 g P per m2 per day.

Beginning in 2002, HydroMentia, Inc., of Ocala, Florida, began building 18-million- to 110-million-lpd ATS units for nutrient scrubbing of agricultural non-point-source wastewaters (streams, canals, and lakes) throughout south Florida. Because these units are modular, with single modules ranging from 3 million to 93 million lpd, any size is potentially possible. Funded by the South Florida Water Management District, a 1-ha ATS system was also built and operated for two years to test the economics of the process. This S-154 unit was used to clean stormwater from a canal just north of Lake Okeechobee in Florida (figure 4). The target nutrient in this case was P, and the stormwater was ultimately derived from agricultural activities, primarily cattle production.

A plot of P removal, compared with P loading for ATS and with the storm-treatment-area-constructed wetlands- the latter extensively developed in the northern Everglades of south Florida-is shown in figure 5. As is shown in the figure, P removal is a function of loading rate (i.e., flow rate and P concentrations). The highest P removal rates in the S-154 system were derived from the most heavily loaded set of experiments (i.e., increased flow rates). These rates were exceeded only by the Patterson ATS system described above. ATS removal capability is roughly two orders of magnitude greater than that of the managed wetlands in the same region.

Nutrient removal with ATS from concentration animal sources

Extensive studies at the US Department of Agriculture's research facility in Beltsville, Maryland, have documented ATS algal productivity and nutrient recovery values using dairy and swine manure effluents. Initial studies using small indoor ATS units (1 m2) and different loading rates of dairy manure effluents demonstrated that algal productivity and nutrient content values of the resulting biomass grew with increasing loading rate up to maximums of about 20 g per m2 per day (10% ash content) and 7% N and 1.5% P (Wilkie and Mulbry 2002, Kebede-Westhead et al. 2003, 2004). More recent studies using outdoor, pilot-scale ATS raceways and dairy manure effluents yielded weekly productivities ranging from 5 to 25 g per m2 per day and averaged about 10 g per m2 per day during a 270-day growing season (April to December) from 2001 to 2006. At loading rates up to 1 g total N per m2 per day, recovery of input N and P in the algal biomass was 80% to 100%. However, at higher loading rates (up to 2.5 g N per m2 per day), recovery of input N and P in the biomass decreased to 40% to 60% (Mulbry et al. 2008a).

Greenhouse studies using dried algae from manure treatment demonstrated that plants grown in potting mixes amended with algae were equivalent in mass and nutrient content to plants grown with an equivalent amount (on an N-availability basis) of a commercially available fertilizer (Mulbry et al. 2006). Dried algae is an excellent alternative to inorganic fertilizers in that it contains no ammonia-N or nitrate-N that can leach into groundwater or be carried away by rainfall at the time of application. Instead, when applied to the surface of or lightly incorporated into the soil, the dried algae breaks down as seedlings grow. About 25% to 33% of algal N becomes plant available within 21 days after application. Extensive analyses of the algal biomass from multiple manure effluent experiments showed that it does not contain heavy metals at concentrations that would limit its use as a fertilizer or animal feed supplement (Mulbry et al. 2006). An economic analysis of a farm-scale ATS system for treating dairy manure concluded that it would be very expensive on a per-animal basis but very competitive with other accepted but less well-documented agricultural best-management practices (Pizarro et al. 2006, Mulbry et al. 2008a).

Nutrient removal from rivers

A large part of the nutrients invested in agricultural production, whether through farm run-off or subsurface drainage, eventually reaches major rivers, where it joins with uncaptured N and P from sewage plants. ATS systems can be applied to US rivers, where total N and P concentrations typically range from 1 to 5 mg per L and 0.1 to 0.6 mg per L, respectively. An 11-billion-lpd engineering plan to clean the entire Suwannee River in Florida of excess nutrients has been designed, and test units are in operation. It is anticipated that in the central United States, ATS systems would develop a mean yearly algal biomass production rate of 35 g per m2 per day. Although extensive field test studies are needed, it seems likely that the north-to-south range of yearly algal production in ATS units used to clean rivers in the United States would be about 25 to 45 g per m2 per day.

During the late 1980s, it was determined that agriculturally derived nutrients, principally P, were seriously affecting the Florida Everglades. In the search for a landscape-scale technology for removing that P from farm run-off, the South Florida Water Management District screened two-dozen technologies and selected nine for further study. Managed, constructed wetlands were eventually selected as the most suitable technology after a decadelong comparison. In an economic analysis published in 2005, Sano and colleagues, reporting for the Institute of Food and Agricultural Sciences of the University of Florida, normalized data from the S-154 ATS test plant as a 23-ha facility over a 50-year operation. It was determined that such an ATS system could remove P for $24 per kg. The ATS cost, per unit of P removed, was about one-third of the least expensive equivalent constructed wetlands module.

In late 2005, the engineering firm Hazen and Sawyer, of Hollywood, Florida, revaluated the S-154 data, with and without pumping and algal harvesting costs. They evaluated several scenarios for the algal biomass, including "giving it away." Using the data for 0.5 mg per L P influent concentration and including one-half pumping costs (for river floodplain operation) and a discount rate of 5.375%, the firm's figures provide a cost of $28 per kilogram P. Assuming this number (Florida construction and labor costs) to be higher than the US average and allowing for a broad range of value in the algal biomass, including energy value, the basic nutrient scrubbing task was accomplished for $24 per kg (with N removed at the same time, for the dollars already invested). Therefore, N and P were removed at a cost of approximately $1.50 and $22.40 per kg, respectively. When the production of the ATS plant is normalized for the lower light and temperatures in the center of the country (e.g., in St. Louis, Missouri), the cost is roughly 20% of the average cost of nutrient removal as it was published by the Chesapeake Bay Commission in 2004 (CBC 2004). Because these analyses attributed all costs to P, the relative costs of the two nutrients are distributed according to the CBC mean proportions.

Bioenergy: Solar energy capture using photosynthetic systems

Given the consequences of carbon release and global warming, the need for renewable energy supplies and especially liquid fuels for transportation has become widely accepted. Although many types of renewable energy are being implemented, including solar, wind, and geothermal, it is widely recognized that biofuels are also a necessary part of developing greater energy self-sufficiency (Tyner 2008). The US short-term answer has been corn ethanol, with the longerterm addition of cellulosic fuels from switchgrass and wood chips. However, as was discussed in a review by Rotman (2008), corn ethanol is probably not economically or energetically viable over the long run; cellulosic ethanol is still in the research phase. Optimistic forecasts predict meaningful production in five years, whereas pessimistic forecasts predict that it may not be economical, suggesting that meeting our national biofuel targets will require further technological breakthroughs.

One answer to the energy dilemma has been microalgal production (Ryan 2009). Experimentally, algal biomass production values can be 7 to 30 times greater than agricultural production values, especially when driven by carbon dioxide from power plant stack gases (Huntley and Redalje 2007, Wang et al. 2008). Some commercial entities have reported 7500 to 22,500 L of biofuel per ha per year in pilot plant operation (Chisti 2007). This compares with 75 to 975 L of biofuel per ha per year for agricultural products from soy to palm. Although there has been clear exaggeration about biofuel yields from algal production (Waltz 2009), this is an active area of renewable energy research.

There are two general approaches to industrial algal production. The oldest and most developed technology is mass culture of suspended algae in open raceways or ponds. This technology is relatively inexpensive (compared with photobioreactors) and is highly productive (up to 30 g dry weight per m2 per day; Goh 1986, Benemann and Oswald 1996, Olguin 2003, Craggs et al. 2003). This approach was pioneered for wastewater treatment by Oswald and coworkers at the University of California, Berkeley, and has been extensively developed in central California. Three algae-based municipal wastewater treatment plants are currently operating in California. The oldest has been in continuous operation for more than 20 years (Oswald 1995, 2003). Clarens and colleagues (2010) conducted a lifecycle analysis using data from the literature for an open-pond algal production system. They found that the algae-to-energy pathway is most favorable when nutrients in wastewater effluents are used in place of commercial fertilizers.

More widely promoted in recent years has been the closed photobioreactor concept, in which selected or genetically engineered monocultures of algae are grown in an interconnected array of clear tubes or bags (Carvalho et al. 2006, Ugwu et al. 2008). Such algal culture is carried out in greenhouses, using a wide range of proprietary technologies to optimize photosynthesis. Greenfuels Technologies has reported a three-month mean rate of production of 98 g per m2 per day in a pilot operation linked to an Arizona Public Service power plant. On 12 December 2007, Vertigro Joint Venture issued a press release reporting a three-month average algal production in a pilot photobioreactor at El Paso, Texas, of 102 metric tons per ha per year (138 g per m2 per day). Although the economics of such operations remain largely unknown, the infrastructure required clearly suggests very high costs if the key environmental and culturally pristine conditions requisite to high production are to be met. Recent estimates of algal biomass production costs for photo bioreactors are about $3.50 per kg (Chisti 2007). Although carbon dioxide sequestration is clearly a favorable feature of this methodology, carbon capture can be only a minor economic element in such a high-cost endeavor. Extensive life-cycle analyses will also have to be performed to determine the net value of fossil carbon kept from the atmosphere per unit of energy produced. Finally, it seems problematic that large volumes of complex wastewater could be efficiently used in a system requiring precision and sterile conditions for production; this suggests that large-scale wastewater treatment is unlikely to be a significant part of any photobioreactor equation.

Biofuels potential of ATS

Tertiary treatment of average domestic secondary wastewater and treatment of moderately eutrophic rivers by ATS in midlatitudes would produce on the order of 18 metric tons (dry weight) of algal biomass per ha per year. This algal biomass would result from treating about 3.7 million lpd per acre of secondary sewage effluent or 18 million lpd per acre of river water, as was indicated by the ATS studies cited above. For the typical large-river nutrient range of 0.1 to 0.6 mg per L of P (with P as an indicator of total nutrient spectrum), the algal biomass produced is likely to be dominated by green algae but to be rich in diatoms. All algal cells have phospholipid membranes and a small amount of oil that can be converted to biodiesel. Diatoms store food in oils, and therefore tend to have higher oil content (some of the "high oil" algae utilized in the US Department of Energy studies of the 1990s were diatoms; Sheehan et al. 1998). Oil extraction of ATS algae has been demonstrated by Midwest Research Institute researchers, who used algal biomass from HydroMentia's Taylor Creek Plant in the Lake Okeechobee watershed. Although it is possible to convert oils from ATS algae into biodiesel, in this article we focus on biofuels from fermentation processes rather than from oil extraction; this is because of the relatively low concentrations of fatty acids in the ATS algae (Mulbry et al. 2008b, 2010) and the relatively higher economic value that might come from conversion of algal oils into nutraceuticals, such as omega-3 fatty acids (Adey 2010).

In 1998, the chemist David Ramey improved the 90-yearold acetone-butanol-ethanol industrial fermentation. Ramey (1998) used two separate species of the anaerobic bacteria Clostridium in a two-step fermentation process, followed by a physical concentration process that produced a 90% butanol product plus hydrogen gas as a byproduct. In a 2004 report to the US Department of Energy, he described a continuous production plant of 185 L per week from corn and dairy wastes and proposed plans for expansion to multimillion-gallon production. Researchers from the University of Western Michigan have analyzed the Taylor Creek algal biomass and produced a preliminary plan for producing butanol (from carbohydrates) from the algal product (table 1). Using the current cost data for a 580-ha, 11-billion-lpd ATS system designed to clean the Suwannee River in Florida, and applying that study to a similar plant in the center of the country, we calculated that the algal biomass substrate available for energy conversion would cost about $0.75 per kg. This compares with recent estimates to produce microalgal biomass using photobioreactors of $3.50 per kg (Chisti 2007), as was noted above.

Although the photobioreactor biomass is estimated to have higher oil content than ATS algal biomass, and therefore to have lower refining costs, the ultimate price of the biofuel produced by the two methods is likely to be about the same: between $1.60 and $2.70 per L ($6 to $10 per gallon). Therefore, growing algae using ATS solely to produce energy-even at large, efficiently operated facilities on river floodplains where pumping costs and energy input are minimal-is not likely to be a profit-making endeavor and would be highly sensitive to the price of crude oil. On the other hand, ATS algae provide a much larger potential for bioenergy supply than corn and soy because of their high productivity. In addition, the value in the nutrient removal process, given as credits or bankable dollars-even at a fraction of the cost of current removal in the Chesapeake Bay watershed, for example-would cover the cost of construction, operations, and maintenance, and still leave a significant profit margin. The recovered oil and butanol would be byproducts available at the cost of refining, very likely at 20% to 30% of current fuel prices. Because the processed biomass would produce a balanced fertilizer, this would provide an additional return. Perhaps most important, the energy product would have little sensitivity to the global price of crude oil.

Conclusions

The use of ATS for water quality improvement is an established practice (Adey and Loveland 2007). ATS was developed through ecological engineering techniques and has been studied for more than 30 years. Commercialization of the technology is under way by HydroMentia, Inc., which is currently building and operating ATS on the hectare scale in Florida. Use of ATS for water quality improvement represents a kind of "nutrient farming" (Hey 2002, Hey et al. 2005), with clean water as a primary output. Values from byproducts of the biomass of algae grown on ATS need to be developed, but these will accrue in addition to water quality improvement values. When scaled up for application to whole watersheds, ATS will generate further value as the basis for a "green economy" with jobs for people who would build and operate the systems and the spin-off businesses that would make use of the algal biomass.

Research to improve the performance of ATS is continuing. Productivity of algae grown on ATS is primarily limited by the interaction of sunlight and temperature, because nutrient-rich waters are used for operating the system. Inputs from industrial power plants (carbon dioxide-rich flue gas and heated water from cooling use) are being tested for their potential to stimulate algal growth on ATS. A recent testing of a three-dimensional screen also indicated increased algal growth as a result of the larger surface area for attachment and support of algal species. Finally, variations on the original floating screens are being developed and tested, which would extend the application of the technology to open-water locations. Because of its modular and flexible design, ATS can be installed in a number of rural settings to utilize wastewaters or polluted water from rivers, lakes, and coasts for multiple benefits.

[Bilk]

Translation?

[Amphiprion]

http://www.nature.com/nature/journal/v458/n7234/full/nature07659.html

A good article. Suggests that there are species of algae that are able to exist in even the leanest P situations. This somewhat fits into the algal succession on scrubbers that I've noted. It also brings into question the whole "if you have algae, nutrients are too high." While I've known for a while how phosphorus works, I still think this statement isn't quite accurate. It certainly doesn't explain the miraculous growth of algae in very pristine locations where there is no cropping or competition.

http://link.springer.com/article/10.1007%2Fs00027-007-0922-1?LI=true

This article suggests that typical criteria for trophic states may not be inclusive enough and that everything may be much more complicated. Makes one wonder what this would mean for the usual ideal trophic designation of a reef would be... as in are they as truly oligotrophic as we idealize them, at least in the traditional sense... Interesting nonetheless and food for thought.

[MorganAtlanta]

Okay... I've waded through most of this thread, and I'm a bit confused as to what the point being discussed is. Is it that harvesting algae from the system does or does not remove *any* phosphorus, or that it does not remove *all* phosphorous, or that it only removes *some* of the phosphorus, and the question is how much?

Arguing that it doesn't remove *any* seems silly, since the algae harvested is made up of organic matter that surely contains phosphorus.

Arguing that it doesn't remove *all* phosphorus, may be a bit silly also, since most tanks have other sinks for phosphorus (Ace25's maybe excepted), this is obvious.

Arguing that it removes only *some*, but the question is how much, seems reasonable, and easy to answer without knowing much about the various fluxes of phosphorous inside the system. That's just a simple mass balance. Measure what you put in the tank as food and measure what you remove from harvesting (and/or skimming, water changes, etc.), and there you go.

What actually happens inside the tank is irrelevant in a first order black box model. Of course, things are more complicated than the black box model, but until someone has done at least that, theorizing and speculating and quoting somewhat related studies from other fields seems less than useful.

[xerophyte_nyc]

Arguing that it removes only *some*, but the question is how much, seems reasonable, and easy to answer without knowing much about the various fluxes of phosphorous inside the system. That's just a simple mass balance. Measure what you put in the tank as food and measure what you remove from harvesting (and/or skimming, water changes, etc.), and there you go.

Yes and no. Simple mass balance would provide us with a net change in P during a set time interval. But it does not take into consideration the P that is being shed by the algae during that time period. The continuous shedding of P just fuels the bacterial-algal cycle.

I don't have the means to figure out exactly how much P is in my food, and then how much P is in the algae that is harvested. I might be able to come up with a rough estimate simply by getting a dry weight of a weekly algae removal, then extrapolate how much P is there by weight, and then further extrapolate how much of a food equivalent it is to see whether P in the algae is the same, higher, or lower. It would be neat if someone could do this accurately.

But there is still the issue of "chasing" phosphates. By the time algae uptakes P, it has already been processed by bacteria, and the algae is also continuously shedding P. It's just not efficient at all, in those cases where the goal is to significantly reduce P. In a heavily fed tank, where one seeks to gain nutrient control, an ATS helps to keep levels from going through the roof. But an ATS doesn't really work towards P reduction over time.

The simple fact that in general we are continuously harvesting algae means there is plenty of P in the system feeding that growth. I am not by any means suggesting an ATS is a bad thing. I'm just pointing out that it is incorrect to say that an ATS will lower net P in a tank over time. It will keep it stable, which for a high bio-load tank is beneficial.

[Garf]

What about Photosynthetically induced phosphate precipitation? This is thought to be a major player in reducing phos levels in the ocean, which may be utilised in the ATS.

[xerophyte_nyc]

What about Photosynthetically induced phosphate precipitation? This is thought to be a major player in reducing phos levels in the ocean, which may be utilised in the ATS.

Thinking out loud here...if pH is high enough to precipitate P out of solution, it would then probably bind to open sites within the substrate (rock or sand). As long as pH remains high enough (I believe around 8.6) then the P is locked up, which would be great - the sand could become a phosphate sink and then it could be replaced. But if the goal is to keep the P safely bound, how do you keep pH elevated consistently, without also considering that calcium will start to precipitate onto equipment? If you are suggesting that locally the scrubber screen physically traps this P, it would make sense - not unlike what I already mentioned about the screen perhaps being a very good detritus trap.

Maybe the ATS is nothing more than a glorified filter sock, trapping detritus and other particles so well that it supports fantastic algal growth.

[Bilk]

Thinking out loud here...if pH is high enough to precipitate P out of solution, it would then probably bind to open sites within the substrate (rock or sand). As long as pH remains high enough (I believe around 8.6) then the P is locked up, which would be great - the sand could become a phosphate sink and then it could be replaced. But if the goal is to keep the P safely bound, how do you keep pH elevated consistently, without also considering that calcium will start to precipitate onto equipment? If you are suggesting that locally the scrubber screen physically traps this P, it would make sense - not unlike what I already mentioned about the screen perhaps being a very good detritus trap.

Maybe the ATS is nothing more than a glorified filter sock, trapping detritus and other particles so well that it supports fantastic algal growth.

This all sounds correct I believe. I think messing with the pH may also disturb the calcification process - it being too high or too low to allow proper calcification.

I've been trying to do some research on why Zeovit systems require a potassium to be as close to 400 as possible. That system relies on a gererally alk level than what many people sun - somewhere around 7dkh. I received a response from one person with this link, which I cannot access. Maybe one of you can access it. It's well above what I would understand any way :) Link (http://www.ncbi.nlm.nih.gov/pubmed/7284321) Somehow this may all tie together. Or maybe not LOL

[Ace25]

I found one way to drop phosphates down to 0 quickly... by mistake. I would never recommend anyone doing what I did because it was a major screw up on my part, but the results were shocking to me.

What I did is I put 2 cups worth of GFO in a BRS dual reactor. Since these reactors suck balls, after the first day the first canister was full of air causing the reactor to not work properly. In the process of clearing the air out of the canisters (turning the valve off/on full blast quickly), I must have left the valve open a little to much which ground up the GFO into dust which then got into my system (couldn't see it, but since there is only 1/4 left in the canisters from what I started with I know it made it into the water). The very next day I came home from work to a huge bacteria bloom in my tank, almost milk white. I panicked, turned off the reactor and did a 20G water change quickly. Next day, water is absolutely crystal clear and my phosphates on that system when from .29 to 0.00 on my Hanna meter (tested 3 times to verify).

I have no idea what exactly happened, I can only guess. My guess is the GFO dust got all over the rocks and substrate and somehow bound up the phosphates that has accumulated (the algae in the display literally melted away overnight and I could see a red tint on the algae from the GFO dust).

The worst part though, I lost 1 fish this morning. It was my oldest fish, a 13 year old yellow wrasse. Not sure if my mistake caused the death because it was already 5+ years past its life expectancy. When I pulled the body out this morning it looked healthy and full (nothing wrong with its skin/eyes/fins and had a fat belly) but the fish has been acting very odd for the past year. The fish turned into a total tweaker fish where anytime I would even walk close to the tank it would freak out and go nuts in the display trying to jump out and scare all the other fish. Either it was just old age or a combination of old age and the GFO dust, but either way while it sucks to lose my oldest fish, I am not too heartbroken because the fish has been causing problems for me and my other fish for over a year now.

[Floyd R Turbo]

How did your reactor will with air? I don't have one of these but isn't it just like a DI canister? Even if you get air trapped in the canister, the water would still get pushed up through the GFO and any air would escape through the outlet. Unless you plumbed the inlet into the outlet, which would trap air in the sleeve insert.

[Ace25]

Hard to describe, but it is the way I have the reactor plumbed into my return line. Any air bubbles that hit the return pump always end up in the reactor and when the first canister outter sleeve is all air it makes the media in the canister behave strange, in turn making the second reactor not move at all. I will never recommend a dual reactor to anyone now that I know the issues with them. Single reactors are the only way to go to ensure they function properly and consistently.

Reactors work just like DI canisters, water comes in and down the outter sleeve and comes up through the bottom of the inner container and out the top. If the flow was reversed it would just push all the media out the bottom of the container, into the outter sleeve, and up into the next reactor.

[Floyd R Turbo]

That's odd. I've never heard of anyone complaining of their dual reactor not working right.

[Amphiprion]

Maybe the ATS is nothing more than a glorified filter sock, trapping detritus and other particles so well that it supports fantastic algal growth.

Well, yes and no. Sure, scrubbers can and do trap particles and to some extent can act as export that way and be supported by it. That is one of the adaptations of filamentous algae that gives them an edge. Filter socks wouldn't be able to increase local pH and system pH, though, and wouldn't be able to induce PO4 precipitation (at least under certain conditions). I suppose a more accurate way to compare it would be somewhat similar to having a filter sock laced with LaCl3 (except potentially more soluble) when conditions are favorable.