Photosynthetically Induced Phosphate Precipitation

[Garf]

Firstly, I would like to thank "BILK" for putting me onto this idea.

Had this flying around in my head for a few days now, and found a link that confirms my thoughts;


http://www.patentgenius.com/patent/5851398.html


It appears that at around a pH of 8.5 (needs to be tested), phosphate will precipitate out of solution, perhaps with some calcium. In normal tank conditions with a pH of higher than 8.5, the precipitate causes a nutrient sink somewhere in the tank. When the pH is then reduced, by bacterial production of Co2 for example, the phosphate is released once again, and the cycle continues.


Be aware that the scrubber screen increases pH at the algae surface through Co2 depletion.


The theory is if the water being processed by the screen has a pH slightly lower than the precipitation pH of phosphate (8.5 ish), the increase in pH on the algae due to photosynthesis will precipitate phosphate ONTO the algae cells for removal when harvesting the algae.


It may be that some scrubbers require no fiddling with to facilitate this (they may be the ones with magical phosphate removal properties). I suggest MOST scrubbers could be improved with regards to phos removal.


I have started to test this by allowing my sump to increase pH to 8.3ish. Of course this means removing my air flow to the screen. My phos level has been almost static for months now, so I should notice any difference easily.

After doing a few searches on this, it seems it's a well known phenomena, which I think should be followed up.

[Floyd R Turbo]

This could be interesting.

[celtic_fox]

So if that turns out to be true, is the moral of the story to harvest Algae during (or etter yet, at at the end) of the light cycle?

[Garf]

Yes, but the screen pH must be above the precipitation pH, whilst the water feed to it must be below the precipitation pH. It may be that the flow over the screen is as important as the intensity of the light in this regard.

[Ace25]

Makes me glad I run my tanks in the 7.8-8.0 pH range. ;) Just tested on the screen, below the screen, and in the next chamber in my sump, all read 8.01 right now.

[Garf]

Makes me glad I run my tanks in the 7.8-8.0 pH range. ;) Just tested on the screen, below the screen, and in the next chamber in my sump, all read 8.01 right now.

Mine is normally just higher than that @ 8.1 to 8.2 and the scrubber is keeping everything static at the minute, with N&P not going up or down. I'm thinking that if this does work, the phos concentration could be manipulated. Lots of people report phos increasing and this may (may not!) have a benefit. It also appears that this effect may be subject to DOC levels in the water also as it competes with the phosphate somehow (perhaps another cause of increasing phos), dunno, I'm not a scientist :). Willing to have a go and see what happens though.

Edit - Its the pH on the algae cell interface with the water that's important in relationship with the water flowing over the algae, if you catch my drift.

[BearHill]

woaw .. Im intrigued! I will be stalking this post! :) Thanks for sharing!

[sklywag]

Will this be posted in the "Scrubbers for dummies" section?

[Garf]

Progress so far - 48 hrs ago, removed the screen aeration. 24 hrs ago, stopped skimmer operation. pH has increased to 8.4 in the sump and have had a 1 DKH alkalinity decrease, so put some bicarbonate in. No magical phosphate drop yet, early days though.

[tebo]

Hi Garf, Is nothing new that I've never had problems with phosphate, in fact converse one here again, in my case the problem was no3

It turns out that my tank has always had a pH above 8.4, in fact the swing is between 8.46 and 8.52, this can be the explanation of why I have no problems phosphate

my phosphates never rise more than 0.01ppm and why I'm fed full since I have few fish and I want to bring up some hard corals

regards

[Floyd R Turbo]

Thanks for the report Tebo. Are you still having Nitrate problems? Maybe the answer is to find a way to lower your pH so that P is available for consumption by the algae, which would in turn lower your Nitrate?

[Garf]

Hi Garf, Is nothing new that I've never had problems with phosphate, in fact converse one here again, in my case the problem was no3

It turns out that my tank has always had a pH above 8.4, in fact the swing is between 8.46 and 8.52, this can be the explanation of why I have no problems phosphate

my phosphates never rise more than 0.01ppm and why I'm fed full since I have few fish and I want to bring up some hard corals

regards

Seems to fit the theory perfectly, thanks tebo. All practical experience is welcomed, it's the truth we are after and if the truth is that algae can remove phosphate without translating it into growth, then that can be a benefit that can be exploited.

[Garf]

Thanks for the report Tebo. Are you still having Nitrate problems? Maybe the answer is to find a way to lower your pH so that P is available for consumption by the algae, which would in turn lower your Nitrate?

Bubbles on the screen seems to allow this pH reduction out of the precipitation zone, if in fact this theory is proved right.

[Bilk]

Firstly, I would like to thank "BILK" for putting me onto this idea.

Had this flying around in my head for a few days now, and found a link that confirms my thoughts;


http://www.patentgenius.com/patent/5851398.html


It appears that at around a pH of 8.5 (needs to be tested), phosphate will precipitate out of solution, perhaps with some calcium. In normal tank conditions with a pH of higher than 8.5, the precipitate causes a nutrient sink somewhere in the tank. When the pH is then reduced, by bacterial production of Co2 for example, the phosphate is released once again, and the cycle continues.


Be aware that the scrubber screen increases pH at the algae surface through Co2 depletion.


The theory is if the water being processed by the screen has a pH slightly lower than the precipitation pH of phosphate (8.5 ish), the increase in pH on the algae due to photosynthesis will precipitate phosphate ONTO the algae cells for removal when harvesting the algae.


It may be that some scrubbers require no fiddling with to facilitate this (they may be the ones with magical phosphate removal properties). I suggest MOST scrubbers could be improved with regards to phos removal.


I have started to test this by allowing my sump to increase pH to 8.3ish. Of course this means removing my air flow to the screen. My phos level has been almost static for months now, so I should notice any difference easily.

After doing a few searches on this, it seems it's a well known phenomena, which I think should be followed up.
You're welcome :) Now if I only knew what you were talking about that would be even better LOL

Even without a scrubber working on the system, we know that higher ph will precipitate PO4 from the water column. That's why people use Kalwasser for their makeup water. Well one of the "benefits" to using it. I'm just a bit confused as to how to control the ph level flowing over the screen. I guess you're suggesting maintaining ph at NWS which rangers from 8.0 in and around reefs to 8.3 in tidal areas. I know from past experience in my system that ph would rise to about 8.21 -8.25 during the lighting cycle and generally that was it. I know some people see a much higher ph during lighting cycles.

I'm really interested and excited to get my system up and running with the scrubber. Tank is filling as I type this :)

[WannaRace]

I'm with you on that, Bilk, but I seriously don't know what any of that means :-)

So, should I be removing the bubbles off my screen? And trying to lower pH or increase pH?

[Garf]

I'm with you on that, Bilk, but I seriously don't know what any of that means

So, should I be removing the bubbles off my screen? And trying to lower pH or increase pH?

Hi WannaRace - The principle here is to never let the pH of the water increase to over 8.5, but get as close to it as possible so 8.4 seems like a good starting point (you may get alkalinity depletion though). So, if that means removing bubbles from the screen temporarily or permanently, then yes. Depending on your system, you may be able to introduce the bubbles during high growth to limit the pH. pH control is the key to this one. I'm sure you probably know that the figure of 8.4 is also where maximum calcification takes place in corals (coincidence ?).

[Bilk]

Hi WannaRace - The principle here is to never let the pH of the water increase to over 8.5, but get as close to it as possible so 8.4 seems like a good starting point (you may get alkalinity depletion though). So, if that means removing bubbles from the screen temporarily or permanently, then yes. Depending on your system, you may be able to introduce the bubbles during high growth to limit the pH. pH control is the key to this one. I'm sure you probably know that the figure of 8.4 is also where maximum calcification takes place in corals (coincidence ?).
For anyone who has knowledge of the Zeovit system, NSW parameters is the target and thus lower ph and lower alk are what's expected as a result. That system manages PO4 export through the use of bacteria fed by a carbon source and then heavily skimmed.

I tried it. It works. It was just not something I could continue to manage at the time. The dosing and the zeolite agitating became problematic for me. It's also somewhat clandestine as there's no knowing what is in the various components. It's a rather paint by the numbers sort of system and if you follow it without coloring outside of the lines, you should be fine. It wasn't for me. I've always been a rebel LOL

[rleahaines]

OK

How do you keep Ph at 8.4 but not higher?

There are buffering agents that say 8.3 on them - supposed to stabilize Ph at 8.3

Then you have lighting, water flow, aireation, etc. etc.

Running a UAS with a air wand gives a lot of air/water gas transference. Running a skimmer would do the same.

If we want to precipitate Phosphate, is the answer running Ph at as close to 8.4 as possible?

This thread brings up lots of interesting questions.

Of course, the key is that we want stability in the tank more than anything.

[Garf]

OK

How do you keep Ph at 8.4 but not higher?

There are buffering agents that say 8.3 on them - supposed to stabilize Ph at 8.3

Then you have lighting, water flow, aireation, etc. etc.

Running a UAS with a air wand gives a lot of air/water gas transference. Running a skimmer would do the same.

If we want to precipitate Phosphate, is the answer running Ph at as close to 8.4 as possible?

This thread brings up lots of interesting questions.

Of course, the key is that we want stability in the tank more than anything.


Im gonna be supplying bubbles on the screen triggered by my pH controller (when I get a new probe). I'm not sure if the carbonic acid produced by Co2 will dissolve the precipitate (if any), so may try triggering the skimmer instead, which may help reduce excess surfactants.

[tebo]

In fact I still have the problem but more controlled, use the combination of vsv with ats, my phosphates remain between 0.00 and 0.01 and my No3 below 2ppm, but if I stop vsv dose, these are triggered to 10ppm, not what shall I do, what's bad vsv and ats, its excess bacteria is notorious in glasses and rock, I think they call mull

Now as it arises, it should lower the pH so that the relationship no3 and po4 more stable in my tank

regards

[iiluisii]

Garf im doing some testing at the momment tell me what you think. Im rumming a full dose of bio pellets im my tank its been 4 weeks im waiting till the 6 or 8th week to make sure the pellets are on full power and then im gonna start my algae scrubber . My belive on this is that the pellets consume all the nitrates and some phosphates so whem I add my scrubber I fill force it to start growing on phosphates and maybe I get lucky and get the magical phosphates removing algae. The scrubber will never have chance to consume nitrates since the pellets consume nitrates at a much faster rate than algae

[Garf]

Been doing a bit more reading;


The first maximum, at approximately pH 8.75, is due to precipitation of P onto and/or into the cell walls of the algal turf, in accordance with the method disclosed and claimed herein. The maximum rate of P removal,at about pH 8.75, was about 0.22 mg/U15 min in this example. The preferred pH range for precipitating P onto and/or into the cell walls of the algae, in this example, ranges from about pH 8.3 to about pH 9.4. The decrease in rate of P removal above the maximum at pH 8.75 reflects the deleterious effects of increasing pH above about pH 8.75 on the efficiency of P removal due to precipitation onto and/or into the cell walls of the algal turf, for this example. The pH of maximum rate of P removal, the slope of the curve on either side of the maximum, and the maximum rate of P removal all may vary with changes in the particular water flowing through the floway. Such changes include variations such as initial pH, salt concentration, nutrient concentration, and the concentration of other species which may have an effect on the algae. The dashed line tailing away from this peak represents the inferred rate of P removal due solely to precipitation of P onto and/or into the cell walls of thealgae as the pH continues to increase.

So, 8.75 is the maximum but benefits increase from 8.3 to 8.75 (the algae cells then attain a pH of 9.9 which causes the precipitation)


a portion of the algal turf is harvested after pollutants, such as phosphorus, have precipitated onto and/or into the cell walls of the algae forming the algal turf. The harvested algal turf may contain atleast 2.0% phosphorus, for example, per unit dry weight of algae. When phosphorus is precipitated according to the invention, the harvested algal turf may comprise at least 1.5% phosphorus in the form of phosphate precipitated on the walls of the algae. In addition, if phosphorus in the form of particulates is in the water, adjustments may be made to algal biomass and/or composition to also trap the particulates. Such trapping would increase the phosphorus content of the harvested algal turf in somesituations to about 5% of dry weight. A significant portion of the phosphate obtained is attributable to the site-specific precipitation action provided by the method of the present invention. The actual level is a function of many variables, including concentration in the wastewater, the relative particulate versus dissolved concentration of the phosphorus, and how the floway operational parameters are controlled. However, of the 5% dry weight maximum amount cited, approximately 0.5% is due to metabolic uptake, at least 2.0% due to precipitation, and at least 1.5% due to particulate trapping. Clearly, the precipitation element is very important to the efficiency of pollution removal on a large scale.

Running this as a precipitation filter alone, could increase the phos removed by 400% + any trapped particulates.
Running the screen effluent through some sort of a particulate filter (horizontal scrubber for example) could increase phos removal by 1000%

Now I'm trying to check if any other good stuff precipitates out at the same time (perhaps that's why some screens just don't work)

[Bilk]

Been doing a bit more reading;



So, 8.75 is the maximum but benefits increase from 8.3 to 8.75 (the algae cells then attain a pH of 9.9 which causes the precipitation)



Running this as a precipitation filter alone, could increase the phos removed by 400% + any trapped particulates.
Running the screen effluent through some sort of a particulate filter (horizontal scrubber for example) could increase phos removal by 1000%

Now I'm trying to check if any other good stuff precipitates out at the same time (perhaps that's why some screens just don't work)

You're going to have to translate all of this when you have it figured out :)

[Amphiprion]

Been doing a bit more reading;



So, 8.75 is the maximum but benefits increase from 8.3 to 8.75 (the algae cells then attain a pH of 9.9 which causes the precipitation)



Running this as a precipitation filter alone, could increase the phos removed by 400% + any trapped particulates.
Running the screen effluent through some sort of a particulate filter (horizontal scrubber for example) could increase phos removal by 1000%

Now I'm trying to check if any other good stuff precipitates out at the same time (perhaps that's why some screens just don't work)

Interesting. Where did the numbers come from? Adey? I'm glad to see quantitative analysis beyond the theory Adey proposed to occur. I had a good idea that this may have been occurring in my scrubber system a few years ago.

[WannaRace]

So running effluent through a filter sock, for example? If that's the case, won't that trap all the "food" that we're creating by running scrubbers in the first place?

[Amphiprion]

So running effluent through a filter sock, for example? If that's the case, won't that trap all the "food" that we're creating by running scrubbers in the first place?

Shouldn't be necessary and may not work as well as it may first seem, since it may be able to redissolve in such a situation. Precipitate granules should adhere to the algal strands themselves to some extent or another, as do many particles. As stated already, this would be even more exaggerated in horizontal or slightly more angled setups vs. vertical ones.

[Ace25]

Ummm.. wow? So we are saying a horizontal scrubber may in fact work much better than a vertical scrubber if built correctly? To me this seems like a huge deal if proven to be true.

[Amphiprion]

Ummm.. wow? So we are saying a horizontal scrubber may in fact work much better than a vertical scrubber if built correctly? To me this seems like a huge deal if proven to be true.

Not sure :p. Vertical ones still have their superior features, namely sheer surface area vs. space consumed. I think enough precipitation can be induced in many cases with vertical scrubbers, if that is the end goal. On my last scrubber, I used plain kalkwasser (no vinegar) and system pH always remained high (like 8.4), so I can imagine it was even higher on the scrubber. PO4 was almost always undetectable using Hanna. I simply picked up feeding to force a tiny bit of PO4 to reduce nitrate. A bit lopsided, but not a bad situation to have from what I could tell. Current tank is way too young to make any conclusions, nor do I have any PO4 or NO3 reagents and/or tests left. Honestly, I'm not even going to worry about it unless I start seeing problems start. The only tests I have are calcium, alkalinity, and magnesium.

[Garf]

Ace - i think if anyone needs to increase phos removal rate 10 fold to normal algae uptake rates, there may be a problem lying elsewhere :) The 4 fold increase should prove more than enough to manipulate phos levels as desired. Here's a chart used to prove the principle. You'll notice that it indicates "Average" pH of the process water (not necessarily display water).

http://i1269.photobucket.com/albums/jj597/Garf1971/9989e684cc7772132468c89a915359ef_zpsedc59df8.jpg

[Bilk]

I was thinking that if higher PH water at the surface of the algae will cause more absorption or utilization of PO4 by the algae on the scrubber screen, one can drip kalwasser into the overflow of that is what is directly feeding the scrubber? Is this what's being suggested?

[Garf]

I was thinking that if higher PH water at the surface of the algae will cause more absorption or utilization of PO4 by the algae on the scrubber screen, one can drip kalwasser into the overflow of that is what is directly feeding the scrubber? Is this what's being suggested?

As long as the pH is restricted to below 8.75, as algae suffers above this level, then it's certainly worth testing. Kalk has all the elements, bicarb for algae Co2, high pH, calcium and importantly dirt cheap !

[Bilk]

As long as the pH is restricted to below 8.75, as algae suffers above this level, then it's certainly worth testing. Kalk has all the elements, bicarb for algae Co2, high pH, calcium and importantly dirt cheap !
Kalkwasser has a high PH on it's own. I guess dripping it into the overflow whould result in a reduced PH by the time it reaches the scrubber. However I've read where people utilize kalk with vinegar dosing. Acetic acid would lower the PH of the kalk. I guess the drip would have to be tested and adjusted to the range that's appropriate. Which is? LOL

[Garf]

Found a link with relation to testing this theory in seawater;
http://www.int-res.com/articles/meps_oa/m319p103.pdf

[Garf]

A quick warning regarding low phosphate levels. It appears that bacteria and algae release a compound into the water called "alkaline phosphatase" when they are limited by low phosphate levels. This compound strips phosphates from any organics (food) in the system and then it is available (and testable) for inorganic uptake by any organism requiring it. So in effect, algae can utilise organic P.

[Floyd R Turbo]

Garf, is this in this article you just referenced? I don't recall seeing/hearing/reading that anywhere before. That would certainly explain a few things. It seems that the majority of the reefing community is bent on P=0.0 when they in effect may just be fighting a battle against mother nature's natural system of balance. So even in an algae scrubber is not being used, but instead biopellets or other carbon dosing methods, the bacteria would be consuming Pi to the point of limitation, then releasing chemicals to convert Po into Pi so they can use it?

This means that depending on the system in use, there may really be no feasible way to make P get to 0.00 all of the time since something is always in need of it, and chemically "requesting" it. I keep seeing things like this that steer me towards the thinking that we don't necessarily want P to be zero, we just want it stable. This type of theory would sure throw off a lot of companies who have invested $$ in phosphate reduction media.

[Nick28]

A quick warning regarding low phosphate levels. It appears that bacteria and algae release a compound into the water called "alkaline phosphatase" when they are limited by low phosphate levels. This compound strips phosphates from any organics (food) in the system and then it is available (and testable) for inorganic uptake by any organism requiring it. So in effect, algae can utilise organic P.

so could this possibly denature coral tissue under limited conditions, and slow or stop growth?

[Garf]

Not in that link Floyd, came across it a few times though.

http://www.skepticalaquarist.com/algae-limiting-nutrients


Though the aquarium's plentiful reserves of organic phosphate generally are unavailable to algae and plants, when mineralized orthophosphate becomes scarce, some algae are able to scavenge PO4 groups from organic phosphates by using a metabolically costly enzyme, alkaline phosphatase (http://en.wikipedia.org/wiki/Alkaline_phosphatase). Alkaline phosphatase, which strips phosphate from many organic molecules ("dephosphorylation (http://en.wikipedia.org/wiki/Phosphorylation)" the process is called), is produced in relatively large quantities by planktonic algae in response to low concentration of orthophosphate, the mineralized form of phosphate (http://www.skepticalaquarist.com/phosphate-cycle) that all photosynthesizers use. It's a negative-feedback buffering system: the lower the orthophosphate levels, the more phosphatase is produced. In fact alkaline phosphatase activity is routinely taken by scientists as an indicator of PO4 limitation in phytoplankton communities.

[Garf]

so could this possibly denature coral tissue under limited conditions, and slow or stop growth?

Gonna be spending today finding out more, will keep you updated (if I find anything useful)

[Garf]

Here's one that describes bacterial oceanic production of phosphatase;
http://www.nature.com/ismej/journal/v3/n5/full/ismej200910a.html


Phosphorus (P) is a vital nutrient for all living organisms and may control the growth of bacteria in the ocean. Bacteria induce alkaline phosphatases when inorganic phosphate (Pi) is insufficient to meet their P-requirements, and therefore bulk alkaline phosphatase activity measurements have been used to assess the P-status of microbial assemblages. In this study, the molecular basis of marine bacterial phosphatases and their potential role in the environment were investigated. We found that only a limited number of homologs to the classical Escherichia coli alkaline phosphatase (PhoA) were present in marine isolates in the Bacteroidetes and γ-proteobacteria lineages. In contrast, PhoX, a recently described phosphatase, was widely distributed among diverse bacterial taxa, including Cyanobacteria, and frequently found in the marine metagenomic Global Ocean Survey database. These taxa included ecologically important groups such as Roseobacter andTrichodesmium. PhoX was induced solely upon P-starvation and accounted for approximately 90% of the phosphatase activity in the model marine bacterium Silicibacter pomeroyi. Analysis of the available transcriptomic datasets and their corresponding metagenomes indicated that PhoX is more abundant than PhoA in oligotrophic marine environments such as the North Pacific Subtropical Gyre. Those analyses also revealed that PhoA may be important when Bacteroidetes are abundant, such as in algal bloom episodes. However, PhoX appears to be much more widespread. Its identification as a gene that mediates organic P acquisition in ecologically important groups, and as a marker of Pi-stress, constitutes an important step toward a better understanding of the marine P cycle.

Marine single cell algae;
http://www.int-res.com/articles/meps/164/m164p021.pdf


ABSTRACT: Alkaline phosphatase (AP) activity in marine and freshwater phytoplankton has beenassociated with phosphorus (P) limitation whereby the enzyme functions in the breakdown of exo-genous organic P compounds to utilizable inorganic forms.

Macro algae;
http://www.drtimsaquatics.com/resources/library-presentations/aquarium-hobby/algae-blooms-solution


Among other variables, he measured alkaline phosphatase, which is an enzyme that macroalgae which are deficient in phosphorous produce, allowing them to use dissolved organic phosphorous instead of SRP

[Amphiprion]

A quick warning regarding low phosphate levels. It appears that bacteria and algae release a compound into the water called "alkaline phosphatase" when they are limited by low phosphate levels. This compound strips phosphates from any organics (food) in the system and then it is available (and testable) for inorganic uptake by any organism requiring it. So in effect, algae can utilise organic P.

Yup, I mentioned this on NR on a similar thread and it was glanced over. Not sure where and why so many thought that uptake was limited to inorganic P. Also, it should be localized activity, if not intracellular. It isn't as efficient as in bacteria, but it does happen among other things and is a fantastic survival mechanism.

[Garf]

Yup, I mentioned this on NR on a similar thread and it was glanced over. Not sure where and why so many thought that uptake was limited to inorganic P. Also, it should be localized activity, if not intracellular. It isn't as efficient as in bacteria, but it does happen among other things and is a fantastic survival mechanism.

Strange how things get "glanced over". Surely if this actually occurred then the "food" that so many are keen on keeping, are actually deficient in P.

Edit - what's NR?

[Amphiprion]

It certainly is strange at times...

I wouldn't say they are deficient in P, but rather require more effort and energy to access, which is why it is not the preferred route. Think of it as a last-ditch means of survival, which partially explains algal growth even in self-proclaimed low nutrient systems. Of course, the amount of P that can be extracted at one time varies, as plant-based material (true detritus) takes a lot longer. Many of these systems would grow algae if it were given the ideal conditions we give it, but getting anyone to believe that is hard. Of course, getting someone to believe that many of those pretty Acropora were actually found in lagoons with vastly different conditions would be even harder...

NR is nano-reef. There's a big thread there about algae and phosphate, part of which was carried over on a thread here. I became admittedly hostile to some of the posters, but it had less to do with what they were saying than their affiliation, so to speak. Anyway, that's now ancient history and doesn't belong here, so I won't bring it up anymore.

[Garf]

We all know that scrubbers export N & P, but what is your take on the importance of herbivores ?

[Amphiprion]

We all know that scrubbers export N & P, but what is your take on the importance of herbivores ?

I think they are as important in aquaria as they are in natural systems. It is low nutrients combined with aggressive herbivory that is conducive to coral growth. I think that is a better way to approach the matter rather than starving our closed systems. Herbivores are often abused, though, so I also think it is important to be responsible instead of dumping a bunch of them in vs. available food. I think they are under-appreciated, under-utilized and often misused.

[Bilk]

Not in that link Floyd, came across it a few times though.

http://www.skepticalaquarist.com/algae-limiting-nutrients
So it seems this article confirms why the Zeovit system is so concerned with maintaining potassium levels in the system. Interesting. It's also an easy and inexpensive nutrient to maintain. Testing for it though, is a pain.

[Bilk]

For those that have access to academic literature, maybe someone can obtain this, dissect the information and see if it applies to control of algae in reef aquaria?
Relations between algal populations and the pH of their media (http://link.springer.com/article/10.1007%2FBF00345087?LI=true)

[Garf]

This precipitation reaction can be hindered by numerous dissolved compounds and organics it seems. Would make sense as they also prevent spontaneous precipitation in saltwater.

http://www.nhm.ac.uk/research-curation/research/projects/phosphate-recovery/house/house.htm


A range of other inhibitors have also been investigated such as glucose, fulvic, humic, phytic, citric, mellitic and tannic acids. Generally they act by a "site-blocking" mechanism whereby the inhibitors adsorb at growth kink sites, the extent of the coverage of the sites being consistent with the Langmiur adsorption equation

Im beginning to believe that the Alkalinity Depletion in scrubber tanks is nothing of the sort, but a rapid calcium carbonate precipitation (which includes phosphate). In my "Co2 Turbo" thread, it was assumed that the algae somehow consumed bicarbonate, and providing aeration would reduce this effect by supplying Co2. However, adding or subtracting Co2 from a system cannot increase or reduce alkalinity, it's a scientific fact! My new theory is that the aeration merely prevented screen pH from rising into the precipitation range, thus counteracting "Alkalinity Depletion" or as I now think of it "Calcium Carbonate Phosphate Precipitation".

http://algaescrubber.net/forums/showthread.php?1838-Co2-turbo

[Floyd R Turbo]

Well, as I understood it, the subtraction of CO2 does not directly lower alkalinity (you are right, it cannot) but the limitation of CO2 in the system as a result of algal uptake of CO2 forces it to go to another source, which in this case is Bicarbonate. So aeration with CO2 directly prevents CO2 limitation, which indirectly prevents the algal uptake of bicarbonate as CO2 remains available, thus in the special case of a system with an algal filter present, adding CO2 can prevent the out-of-balance reduction in alkalinity.

[Garf]

Thats what i thought also. I think what actually happens is that the screen increases pH by removing Co2 from bicarbonate creating carbonate, but then upon aeration and bacterial activity the Co2 is recombined with the carbonate to reform bicarbonate, and once again reduce pH. Therefore no net loss of alkalinity, at least that's how I see it today :)

[Amphiprion]

This precipitation reaction can be hindered by numerous dissolved compounds and organics it seems. Would make sense as they also prevent spontaneous precipitation in saltwater.

http://www.nhm.ac.uk/research-curation/research/projects/phosphate-recovery/house/house.htm



Im beginning to believe that the Alkalinity Depletion in scrubber tanks is nothing of the sort, but a rapid calcium carbonate precipitation (which includes phosphate). In my "Co2 Turbo" thread, it was assumed that the algae somehow consumed bicarbonate, and providing aeration would reduce this effect by supplying Co2. However, adding or subtracting Co2 from a system cannot increase or reduce alkalinity, it's a scientific fact! My new theory is that the aeration merely prevented screen pH from rising into the precipitation range, thus counteracting "Alkalinity Depletion" or as I now think of it "Calcium Carbonate Phosphate Precipitation".

http://algaescrubber.net/forums/showthread.php?1838-Co2-turbo

That's spot on with what I've been observing. One of many reasons why I'm reluctant to try a skimmer again.

FWIW, CO2 in the right situation can be limited pretty easily. I've always been able to do it with strong photosynthesis, whether macrophyte or algal, and running kalkwasser 24/7 (without vinegar, which would increase CO2 in the end). That's when I start seeing an increased carbonate alkalinity demand and a bit more precipitation, like in pumps and on heaters. It is likely a combination of both algal assimilation and a result of precipitation, just based on observations. I think if given the above situation, you could probably look at the scrubber during lighted hours under a microscope and see some calcium carbonate granules that weren't necessarily introduced from sand. I don't think all the sediment my scrubber captures is detritus-based alone, to be honest.

I have no problems with inducing this, as alkalinity is easy and cheap to keep track of. If one has dosing equipment available, it is as easy as adding either dissolved dilute carbonate or bicarbonate (or both) at regular intervals to keep up. Not to mention it provides a new sink for phosphorus export, which is a good thing, IMHO.

[Garf]

Actually, I like the aerated approach as it should be purely algal growth that's taking up the nutrients. In my tank it's stable when aerated.

[Floyd R Turbo]

I didn't think about this until just now. For a period of time, on the tank I run an L2 on, there were occasionally chunks of some calcified substance that seemed to be "stuck" in the screen, near the slot pipe. It seemed rather odd to me at the time that something the size of a grain of reef sand (about 2mm) would make it through the pump strainer and get snagged on the screen. I will watch for one of these things. Could that possibly be a buildup of a calcified deposit due to this precipitation, in a week's time? I would also occasionally notice what looked like grains/chunks in the algae mat.

Will definitely keep an eye out for this...

[Garf]

I seem to remember the phrase "Stiff Algae" on a number of threads. Mines lush and soft, like an expensive green carpet.

[Nick28]

Scrubbers only borrow bicarbonate. hydroxide is released and forms new bicarbonate on contact with Co2. You should have better growth with more alkalinity. Any loss is due to calcification or precipitation.

[Bilk]

Hmmm. I was hunting and pecking around the net. I found this site and this article. Nitrate (NO3) and phosphate (PO4) don’t cause algae. Ammonia does!! (http://aquarium-fertilizer.com/nitrate-no3-and-phosphate-po4-dont-cause-algae-ammonia-does) Now I know what I'm going to hear in terms of it's supporting evidence, but can one of you more scientifically inclined confirm or deny the idea that ammonia contributes to algal growth? Or that according to the article, ammonia is the driving nutrient for it? Does detritus release ammonia into the water column? Decaying matter does so I assume detritus will as well.

I do have to say, I think we have all seen or heard about very successful tanks where the operator is utilizing a water source other than RO/DI or any type of purified water. I've especially seen tanks from the Far East where the person says they used tap water as it's fed by wells or springs and they don't test it. I've even seen tanks that look very successful where the owner says they don't test for anything. It's probably safe to guess that their tanks have PO4 present and their water supply may very well have it present too.

I guess where I'm going is, more importantly than trying to fight what may be a losing battle with nutrient buildup of NO3 and PO4, better husbandry and better water flow, preventing settling out of particulate matter, are probably the reason these other tanks are not dealing with algal blooms no matter what their other nutrient levels are. The release of ammonia from decay is the real culprit and not necessarily the presence of the other two.

As we increase the number of fish and livestock, feeding goes up and residual foods find their way to places and decay. So ammonia is always being released into the water column.


I guess I need to read Randy's article (http://reefkeeping.com/issues/2007-02/rhf/index.php) to get a better understanding of something I thought I understood :) NH4 could be the culprit and not necessarily PO4.

[kotlec]

"It has not been established in a reef aquarium setting, however, what portion of the macroalgae's nitrogen uptake is ammonia and what fraction is nitrate."

From that Randys article

[Bilk]

"It has not been established in a reef aquarium setting, however, what portion of the macroalgae's nitrogen uptake is ammonia and what fraction is nitrate."

From that Randys article
Basically that means no one knows what is what :)

There's a lot of death and decay in a reef tank. The nitrogen cycle is responsible for breaking down the harmful elements of the cycle, but that still leaves a lot of residual nutrients in it's wake. Then we try to export NO3 to undetectable levels. I know things are happening in anaerobic zones, but that uptake happens in a longer duration of time. In many ways, the water column is the filter and the source, and things die in the anaerobic zone too that need to be exported as well.

I don't know, but for some reason I think we're looking in the wrong direction or at least not seeing the whole picture when just considering PO4 as the reason for macro algae. If you notice, algae thrive in the areas of the tank that have the highest flow. The glass generally has the highest flow as that's where the water is directed. Free ammonia is converted to ammonium because of the PH (my understanding of this) then it's still in the water column until something utilizes it. We test and claim that once ammonia reads zero then the tank has cycled, yet ammonia is always being produced. If we diminish the nitrosomonas bacteria to a certain point, then there's not enough to uptake the ammonium and algae then utilize it. How many times have you read 0N and 0P and someone complaining about algae issues?

I think there's something to this, but I have a very limited knowledge base in this area to understand it LOL

[Nick28]

How many times have you read 0N and 0P and someone complaining about algae issues?

could be localized (snail poop) I can see it sticking to algae in my tank giving plenty of nutrients.

[Garf]

I don't think we are only concerned with phos, it's just that phos and other certain elements can be precipitated out of solution on photosynthesising algae (it seems). Therefore we may be able to increase phos uptake / removal when required.

[Bilk]

could be localized (snail poop) I can see it sticking to algae in my tank giving plenty of nutrients.
LOL well snail poop is waste that further decays and releases ammonia into the water column. If it were suspended and then exported out of the tank and the system, then it wouldn't cause algae to grow in that poop spot :)

I know this is anecdotal, but my first venture into saltwater reef keeping was back in the 1980s. I had a 110g with lot's of leather and polyp corals and a few LPS - actually had a euphyllia grow to massive proportions. Anyway, it was still a fledgling hobby then, so the information was lacking and or being produced and revised often. I was running a plenum with a DSB. Thinking back, the tank never really experienced any sever outbreaks of alga. To boot, I used NYC tap water for everything LOL RO/DI wasn't talked about much then other than to utilize "purified water". There were times I would buy gallons of distilled at the supermarket, but then would get lazy and just use plain old tap water. The tank thrived for almost ten years before a move to a new house and other circumstances caused it to crash. Now I'm not sure whether it was the DSB/plenum combination or the NYC tap water that made it as stable and successful as it was LOL

I missed making my point in this post - NYC tap water = nitrates and phosphates right out of the tap then you have what ever is produced in the tank, yet no appreciable algae presence.

[Bilk]

I don't think we are only concerned with phos, it's just that phos and other certain elements can be precipitated out of solution on photosynthesising algae (it seems). Therefore we may be able to increase phos uptake / removal when required.
But maybe it's treating a symptom and not a cause. Yes alga utilize PO4, but they also utilize other nutrients. Now we need to understand which are preferred and which are readily available.

What happens to all the ammonium/NH4 that's created in the tank if the nitrosomonas bacteria population is depleted?

[Amphiprion]

Scrubbers only borrow bicarbonate. hydroxide is released and forms new bicarbonate on contact with Co2. You should have better growth with more alkalinity. Any loss is due to calcification or precipitation.

Duh, I can't believe I didn't think about this. I guess I should've at least thought about the equation.

[Bilk]

After reading a thread on RC about sand beds I'm totally confused and equally totally sure that trapped nutrients from detritus are the reason people experience problems with algae. Now the question is, which nutrient is the problem. Now if nitrates and phosphates read zero, there must be something else feeding the algae.

I love the look of sand but now I'm rethinking what I will do. I can still siphone it out :(

[Nick28]

Duh, I can't believe I didn't think about this. I guess I should've at least thought about the equation.

I don't want to hijack this thread but

I'm not really sold on the bubble rubbing thing I think flow is more useful for two reasons more bicarbonate and nutrient delivery + no light blockage from bubbles. My UAS just has a powerhead on it.

http://reefkeeping.com/issues/2006-10/rhf/index.php#21

This is a really good read on PH, photosynthesis, Co2 and algae.

[Garf]

Some pollutants in the form of elements and compounds that may be precipitated from water according to the present invention are indicated below:

Alkaline Earth Metals

Magnesium, Calcium, Strontium, Barium

Heavy Metals

Titanium, Chromium, Molybdenum, Nickel, Copper, Zinc, Vanadium, Mercury, Cadmium

Metals

Manganese, Iron, Cobalt, Lead, Boron, Aluminum

Prime Nutrients

Phosphorus, Sulfur, Carbon, Nitrogen

OK, so lots of this precipitation is definately good. however, there are a few on the list that are not tested for regularly. Are we sure that the essential elements that may be precipitated are delivered back into the aquarium by feeding and dosing etc, in high enough levels? A low level waterchange protocol would be advisable surely.

[Amphiprion]

Do all the elements in question necessarily need to be added back? What purpose do some of them serve? What concentrations are they present in artificial salt mixes to begin with? I think I'd rather take my chances without adding them back manually and do a very occasional small water change just in case--say a few times per year. I don't feel like spending that much on ridiculous quantities of salt mix in order to change water constantly like many do.

[Garf]

It may be that none of them are really important, other than the obvious ones like cal, mag etc. as there may be a certain input made by feeding etc. however a 1% monthly waterchange or so should guarantee its inclusion in the tank IMO.

Just a reminder that NONE OF THIS THREAD APPLIES to systems that maintains its scrubber water pH at below 8.3., at all times.

[Garf]

Screen clean today and I've got sparkly bits;
http://i1269.photobucket.com/albums/jj597/Garf1971/57624f05b7e61552fb662b08a3aad96e_zps0aaafa37.jpg
http://i1269.photobucket.com/albums/jj597/Garf1971/0edc45c80522a78a1ce8fdc6c2a8638d_zpsf9510628.jpg

[xerophyte_nyc]

After reading a thread on RC about sand beds I'm totally confused and equally totally sure that trapped nutrients from detritus are the reason people experience problems with algae. Now the question is, which nutrient is the problem. Now if nitrates and phosphates read zero, there must be something else feeding the algae.

When you say phosphates are zero, what you really mean is inorganic phosphate is zero. Hobby testing kits don't analyze the organic P in the tank. Inorganic P can be consumed so quickly that you can't test for it. At low levels it is used up (by photosynthetic life) almost as quickly as it is made. Detritus has organic P within it, so when it lingers around in the tank, bacteria will metabolize it and create more inorganic P.

You are right about detritus being a big problem in our tanks. What makes it an even bigger problem is we can't measure it. It's easy in the ocean, nutrients get diluted and washed away. We can't do 100% water changes every few hours without plumbing your return line to the ocean. :D

[Garf]

A few results;

1] phos is definately going down
2] discolouration in the water has disappeared (I've always had a tint in the water, only visible under blues)

I was hoping to keep this next fact for a future testing but I feel it's too pertinent to this thread. Phosphate precipitates out at 9.9 pH (fact), dissolved organics flocculate into skimmable and trappable particles at pH 9.7 !!! (fact) So I don't think I'm over exaggerating when I say that running a scrubber with water around the 8.3 to 8.6 range (the rest of pH increase is at the photosynthetic surface) reduces phos levels and strangely dissolved organics, maybe even more effectively than a skimmer, especially in slower running water, ie with thicker screens. Any thoughts welcome.

[Floyd R Turbo]

Garf remind me how you get your pH to stay so high all the time?

Also like I mentioned before I have had those chunky bits on the screen/algae mat on my L2 with tank pH below 8.0. So I don't know what that says.

[Garf]

Garf remind me how you get your pH to stay so high all the time?

Also like I mentioned before I have had those chunky bits on the screen/algae mat on my L2 with tank pH below 8.0. So I don't know what that says.

Well, its not high all the time. Im aerating the screen for 4 days, then no bubbles for the last three days. I've got a very slow running sump (about 300 or 400 lts hr), so the scrubbed water recirculates over the screen more than most, which gets the pH to rise. Along with that, Kalk additions increase pH. I had some glistening waxy deposits in between some of the algae strands on the last clean. The day before cleaning, I am running the scrubber lights for 36hrs non stop to keep the pH in the upward direction prior to harvest.

[Garf]

Similar reduction in phos levels this week, barely detectable on the Red Sea test I'm using. This would indicate that i can still run the screen aeration, and increase the "free food" supply for 80% of the time. Harvesting later, then back on with the screen aeration. If I don't get excessive frothing of the sump, this would indicate (to me) that the DOCs have been flocculated and trapped by the screen, or at least turned into particulates (critter food ?) instead of dissolved organics. Doing a 5% per month waterchange to minimise the risk of precipitating out any essential elements from the water column.


http://i1269.photobucket.com/albums/jj597/Garf1971/f61594c1f176a171b068db512cd54cca_zpsce256efa.jpg

[Garf]

BIOGENIC DECALCIFICATION, that's what this precipitation is caused by, and the process by which algaes remove Co2 from bicarbonate, been around a while;

http://www.thekrib.com/Plants/CO2/decalcification.html

[Garf]

Evidence that the increased pH actually binds organics, hence trace metal complexes etc to the precipitation;

http://wap.aslo.org/lo/toc/vol_15/issue_4/0633.pdf

this confirms my observations on my own tank.


Organic compounds may be precipitatcd because the increased pH causes a decrease in their solubility, or they may be removed from solution by association with the few Ca.C03 nuclei that form early in the experiment (Fig. 2.). In either case, organic compounds are removed from solution before rapid CaCOs precipitation occurs

however, if the concentration of organics in the tank is too high, the precipitation does not occur. In cases of rising phos levels, either skimming or activated carbon should be used to reduce organics, therefore allowing the precipitation to occur;


Consequently, rapid CaCOn precipitation does not occur until these organic compounds are removed from solution