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Thread: Scrubbers DO NOT export Phosphorus

  1. #11
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    Exactly. The oceans have there own export mechanisms. Replicating this in a glass box means skimming to a greater or lesser extent.

  2. #12

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    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?

  3. #13

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    Quote Originally Posted by celtic_fox View Post
    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?

  4. #14

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    Quote Originally Posted by celtic_fox View Post
    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.

  5. #15

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    Link to original work: The Oceanic Phosphorus Cycle

    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, on this forum.

  6. #16

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    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?

  7. #17

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    Quote Originally Posted by Nick28 View Post
    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.

  8. #18

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    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.

  9. #19

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    Quote Originally Posted by xerophyte_nyc View Post
    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.)

    Quote Originally Posted by xerophyte_nyc View Post
    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?)

  10. #20

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    Quote Originally Posted by xerophyte_nyc View Post
    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.

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