the Standard Model of Aquarium Algae? ...and, algae scrubbers are fatally flawed

[Totoro]

Whoever it is that's been going into every thread I post in and rating it five stars -- well, first off, thanks for that, but also, you may find this interesting:

 

http://algaescrubber.net/forums/showthread.php?2208-cyano-scrubber-and-also-mud&

 

I also feel I should say a couple of things to the Pacific NW Marine Aquarium Society...

 

First, thank you for tolerating my lectures while I've been thinking this through. No, I don't have a book deal or a product to promote or anything of that sort -- I'm a hobbyist, just like you, except I'm more interested in the stuff you can't see in a fish tank than the stuff you can.

 

And secondly, I apologize for not pointing out earlier that algae scrubbers can't keep up with P input in fish food, and thus scrubbers cannot prevent "Old Tank Syndrome" and a system crash due to P accumulation in the substrate. I caught on to the problem a while ago but thought it would be unkind to harangue poor Kia over this, so I waited until a possible solution dawned on me and then, in what was meant to be a gesture of respect, made my case directly to SantaMonica in his algae scrubber forum.

 

SantaMonica appears to have opted out of the discussion, which suggests to me that either he is unable to refute my position or he was already aware of the problem and just hoping against hope that nobody else would catch on, so I now feel it is appropriate to bring this to the attention of others.

 

And as the title of this thread suggests, I also posted what I tentatively call the Standard Model of Aquarium Algae in that thread, and the Standard Model should be of broad interest to hobbyists -- if, of course, I've got it right -- so I encourage anyone who finds my ramblings interesting or enlightening to take a look.

 

Finally, if anyone out there can drive a truck through the Standard Model, please do so loudly and publicly. I enjoy staring at my fish tanks and trying to figure out what's going on in there, and coming up with the Standard Model was like reaching the last page of a good book...

[kriz2fer]

Those are some nice reads. It good to have people always questioning the normal belief.

[Jeramy]

Just wondering I am not sure that you could not achieve the same results running GFO in a reactor. Could you not do a algea scrubber and GFO to achiev the balance you are looking for or use biopellets and GFO or macro algea and GFO?

[Totoro]

Much the same question was asked in the other thread, Jeramy, and this is my response:

 

The name of the game is bioremediation. If you're satisfied controlling P through chemical means, I'm not going to tell you you're wrong, but please understand that from my perspective, that method is philosophically unsatisfactory. It's also energy-intensive (I'm speaking more of the manufacturing process than the implementation) which expands the carbon footprint of a hobby that's already pretty resource-intensive, and from a more practical standpoint, it can get pricey over the long haul.

 

Plus, as Floyd pointed out in the other thread, even the manufacturers acknowledge in the fine print that chemical scrubbing is more about controlling P in the water column than mitigating P accumulation in the substrate.

[Blackhand]

so if your not for scrubbers or other means of controlling p that are traditional how do you suggest controlling p within an aquarium thanks

[MVPaquatics]

Fequent water changes and light stocking/feeding coupled with good flow and adequate filtration always helps me

[kriz2fer]

Carbon dosing and gfo are the best way. Ats are pretty weak at removing much of anything and the sam can be said for a refugium with a little ball chaeto. Most of the refugiums you see hobbyist use are small Little sections in there sump with a small Bundle of chaeto, in order for a fuge to really be effective if needs to be a whole lot bigger then what most people use. If you really want a clean system you need a good skimmer and some form of carbon dosing along gfo and water changes.

 

Don't get me wrong, you can have a successful Sps tank with out carbon dosing but most of the

Time you will be battling po4 and nitrates often.

[Electrokate]

or we could also try not freaking out over a little algae, as long as it's a little. Beats dinoflagellates by a long shot (: When I have non fish people over they think cyano and valonia are cool. I don't think they are at all cool mind you but I am willing to question my need to totally control that which probably cannot be controlled, and maybe ought to be considered part of the whole system in a normal tank. I'd love to have one of the superclean massively grown SPS tanks I see on forums featured as tank of the month but I accept that I am not willing to spend the time, money and expanded carbon footprint it takes to achieve those results. Diminish my expectations a little and I can relax a lot, and achieve realistic goals. Also read a study that SPS grow faster with phosphate. Scientists were intending to show how fertilizer runoff stunts reefs. Oops. Downside is phosphate enhanced growth produces lighter, less dense and more fragile skeletons. Mushy SPS. So I guess they proved their point in another way... the ocean is too rough for weak skeletons

[MVPaquatics]

Let me also say it is very refreshing to see such thought and knowledge going into your posts and responses totoro. I have always pondered a cyano scrubber of sorts but on a much more simplified basis, kind of a fight fire with fire kind of thing. I for one appreciate the time and energy that you are giving to take it to a new level

 

Just out of curiosty, you touched a little on how iron fits into the mix...anymore info on that?

 

And on a side note, I totally agree about hobbiests not wanting scientific literature quote, they are into see it to believe it. Great read!

[Electrokate]

I too am a ponderer and type 70wpm, people often tire of my long posts. One of my favorite books is Plankton Culture Manual. I like geeking on the science behind this hobby. So am on your side too. We can always learn more.

 

Also interested in hearing about iron dosing. Did that for a while, ran out and forgot about it. One of my friends was among the first people to keep flowerpot corals alive, he swore it was the iron dosing that did it.

[Derbird]

Thank you for posting this up. I am still trying to learn about the scientific side of our hobby and this brought up many new things to think of.

 

I have a most likely silly question :o. How do you avoid the "old tank syndrom"? Which if I read right is a build up of PO4 in the sand bed. Do I need to change out my sand bed from time to time or is there a better way. My sand bed just turned a year old. I do have sand sifting critters but never thought of a PO4 build up before. The sand varies from 1/2 to three inches depending on where my dragon goby has done his job.

[Totoro]

Iron. Right. As micronutrients go, that's a big one.

 

I do have a couple of pieces of good information on how iron affects the structure of algae communties. First, cyano needs Fe in a big way because the enzymes involved in fixing nitrogen are known to be very iron-rich, and growth using N2 as a nitrogen source can require as much as 10x more Fe than autotrophic growth using NH3 to supply N. Autotrophic growth on nitrate also requires iron-rich enzymes to convert NO3 to NH3, BTW, but less so than cyano.

 

Iron is the only micronutrient known to be limiting for marine phyto in the wild -- one estimate suggested that phyto is Fe-limited in as much as 40% of the ocean's surface waters. Iron is so important that when it's the limiting nutrient, bacteria (including cyano) and some algae secrete what are essentially tiny chemical nets, called siderophores, around themselves to sweep up iron from the water atom by atom. Neat, eh?

 

Organisms without siderophores are adapted to capture iron that's complexed with organic molecules. Broadly speaking, then, iron complex supplements should favor green algae. Electrokate, I would speculate that the algal symbionts inside corals can't form siderophores -- what good would they do in there? -- which could explain why corals might benefit from iron complex supplements. A chelated iron supplement, however, would probably not provide any benefit, as the whole problem with obtaining iron in the wild is that in NSW, what little Fe is available to begin with mostly gets locked up by chelation. In the absence of any other information, this might explain anecdotal, hit-and-miss success with iron dosing.

 

 

How do you avoid the "old tank syndrom"? Which if I read right is a build up of PO4 in the sand bed. Do I need to change out my sand bed from time to time or is there a better way.

 

Yes, you change out the sand bed -- not all at once, though -- and soak the LR one piece at a time when rising P becomes an issue. Should take several years in a well-run tank, though, so don't panic. And probably most tanks don't stay up that long, anyway, so it's a non-issue for the majority of hobbyists.

 

I've read online about people considering modular remote DSBs so part of the sandbed can be changed out every year. Don't know if anyone's actually built such a thing, but I acknowledge that this type of thinking is where I got the idea for a "remote deep mud bed" to pull P out of an existing substrate.

[pledosophy]

I have been in the hobby a long time now, always a more biology less technology kinda guy. I don't run skimmers, I do 20% water changes every 6 months or so, I am a few months behind. I was originally introduced to reefing by Leng Sy, the refugium guy so for the most part I have run my systems for the last 12 years through a natural export philosophy, but for more reasons then just nutrient export. I respect your curiosity and I have a few basic questions for you.

 

So my sand bed gets full of phosphate, and I use algae to export that nutrient. Why would the algae just not absorb the added phosphate from the sand bed when and if it started leaching? Phosphate+Nitrate= algae for the most part. Why would the natural process not work with stored P.

 

Regarding changing the sand bed every few years. This is a very old school line of thought in my eyes. I am very happy with my well established sandbed and the benefits it provides with the anerobic bacteria that participates in the nitrogen cycle, as well as the micro fauna it produces. If it is just phosphate that is the fear here, are there not less expensive ways then replacing the sandbed? GFO is still cheaper then new sand.

 

In reference to removing the live rock every few years, it kind of goes against the whole constructive ecosystem standpoint. If your rock is absorbing phosphate and your goal is to control the tank using biology at that point would you not just increase your algae population, or change your pruining style to increase growth (i.e. cutting the runners several times instead of yanking to expedite growth in species like prolifera or taxifloria). IME many hobbyists try to starve out certain strains of algaes, they have shown themselves to be very adept at finding and removing even undetectable levels of phosphate and nitrate.

 

Your question if a remote DSB was ever constructed, several have been. They were the rage for a year or so. I believe it was Shimeks writing about the lack of overall value they would have if the footprint was less then 4 foot by 2 foot and the depth was less then 18", however many people using a 5g bucket on a 100g or so system reported great results. Best reported results came if the bucket was covered and no light was allowed in. An increase in food production from the bed was increased as was the nutrient absortion with an increased size of the bed. Several reefers used 55g Rubbermaid trashcans with a couple of bulkheads inline with there sump feeds, some still do. There were some people who adapted these style of sandbeds into modular units by tying multiples together. I tried this myself but never found much benefit likely IMO because of the already large population of algae that I use in my systems.

 

JMO

[Blackhand]

this is a fascinating thread cause i dont know much but my way of thinking was always with yours pledosophy i know that every system is different and we all have different ways of doing things and that will never change and i agree that many people go with the norm and that can be good and bad at times i have too thought of doing a dsb at one time still might but hoping to see more through this thread about more info on ideas just hoping that everyone will understand that there really is not just one way of keeping a successful reef tank everyone has there own ideas and ways of making it their own tank and thats the point isnt it to have your own part of the ocean in your house well thats the way i see it anyways

[Totoro]

So my sand bed gets full of phosphate' date=' and I use algae to export that nutrient. Why would the algae just not absorb the added phosphate from the sand bed when and if it started leaching? ... Why would the natural process not work with stored P.[/quote']

 

It totally does. A substrate leaching P is generally a recipe for a cyano bloom: http://www.pnwmas.org/forums/showthread.php?31036-Cyano-bactiria&p=300357&viewfull=1#post300357

 

Let it bloom, remove it; repeat until it pulls enough P out of the substrate to lose its competitive advantage and stops blooming. That looks like a viable avenue for nutrient export. In fact, that's the first thing I suggested be tried to determine if a cyano scrubber could work: pick a spot where cyano wants to grow, anyway, and start helping it instead of fighting it. Let's see if we can actually grow enough of the stuff to make a difference.

 

The idea of a cyano scrubber is nothing more than to set up a special corner of the system just for cyano, where it'll be so happy that it grows there all the time... Think of an algae scrubber as a permanent, artificially maintained algae bloom.

 

 

In reference to removing the live rock every few years' date=' it kind of goes against the whole constructive ecosystem standpoint.[/quote']

 

I agree. That's why I'd like to find a way to avoid it.

 

Bioremediation (a cyano scrubber) is my first choice. Failing that, I'll try going with simple chemical equilibrium (a remote deep mud bucket). Plan C is soaking my LR.

 

Well, actually, Plan C is probably shutting down and trying something new. I really only set up the marine tank for curiosity's sake, and it's pretty well served its purpose at this point, I must say...

 

 

Phosphate+Nitrate= algae for the most part. ... If your rock is absorbing phosphate and your goal is to control the tank using biology at that point would you not just increase your algae population' date=' or change your pruining style to increase growth[/quote']

 

No disrespect intended, but the Standard Model says algae is not about addition. It's about ratios. I'm obviously not the first hobbyist to catch on to this: http://www.barrreport.com/showthread.php/4018-Comparing-N-P-ratios-and-critical-cocnetrations-in-aquatic-plants-algae?

 

The N:P ratio is the heart of the problem. Broadly speaking, the cells of phytoplankton are the richest among the primary producers in nitrogen and phosphorous, followed by the "higher plants" (marine and FW angiosperms) which are substantially poorer in P and somewhat poorer in N content than phyto, and macroalgaes have the lowest N and P content of all aquatic plants, with an average C:N:P of 550:30:1 and an average protein content of less than 1/3 of phyto's average of 50% protein. Note, however, that the phytoplankton divide between true algaes, with N:P ratios of 20:1 or more, and the cyanobacteria, with N:P ratios of 10:1 or less (...though it wouldn't surprise me if a few organisms prove to be exceptions to this tidy division, like for example a P-rich algae -- BBA seems an obvious candidate).

 

The upshot is that the N:P ratio of green algae (especially tropical macroalgae, FYI, which have an average N:P ratio of over 40:1) is higher than the food going into an aquarium (which I'm assuming is 16:1 -- the Redfield ratio -- but may well be enriched in P, what with amino acid supplements and whatever else people are feeding their corals and blending into their fish foods). This means that green algae cannot mitigate P accumulation without supplemental N, and therefore over the long haul, green algae cannot prevent a tank crash due to P saturation. Doesn't matter how much algae you have or how fast it grows. If the N:P ratio of what you're using to export nutrients is higher than the N:P ratio of what's going into the tank to feed the livestock, you're going to be left with surplus P. However it's executed, I believe the concept is, as the title of this thread suggests, fatally flawed -- it's possible run a balanced system with regards to N using green algae, but not P.

 

Cyanobacteria can fix N, so it'll grow in N-limited environments like a system based on green algae where N is well controlled, and cyano has an N:P ratio lower than the food going into the aquarium, making it a viable choice for P mitigation. So, yes, the goal is very much to increase the algae population, but we need the right algae...

 

 

Your question if a remote DSB was ever constructed' date=' several have been. ... There were some people who adapted these style of sandbeds into modular units by tying multiples together. I tried this myself but never found much benefit likely IMO because of the already large population of algae that I use in my systems.[/quote']

 

Ah, thank you -- I know remote DSBs were The Next Big Thing a while back, but I was never sure if anyone actually tried modular RDSBs. Interesting that it was modular Rubbermaid trash cans, though, as when I mentioned a modular RDSB, I was thinking more along the lines of the modules being some five-gallon buckets submerged in a plastic horse trough or an old 75 gallon glass tank, for reasons that will become clear (I hope!)...

 

 

I believe it was Shimeks writing about the lack of overall value they would have if the footprint was less then 4 foot by 2 foot and the depth was less then 18"' date=' however many people using a 5g bucket on a 100g or so system reported great results. Best reported results came if the bucket was covered and no light was allowed in.[/quote']

 

This looks a bit like a straw man to me, but what the heck... Nobody's taking a run at the Standard Model, so let's kill some time thinking this through.

 

First off, let me make clear that I'm not advocating some particular method of tank management involving deep sand beds... Derbird asked a specific question, and I gave him a specific answer. I do not maintain it is the only viable answer, and I just mentioned DSBs conversationally in reference to the "remote deep mud bed" I described in the thread over at algaescrubber.net: http://algaescrubber.net/forums/showthread.php?2208-cyano-scrubber-and-also-mud&

 

DSBs are (or were) made with relatively coarse sand in order to facilitate the movement of water and nutrients into the DSB. IIRC, pool filter sand was the medium of choice, and from what I remember reading about the guys who were trying to turn old 55G tanks into RDSBs, they all plumbed them to flow end-to-end, thinking they'd maximize contact time with the sandbed as the water passed through. But I think the pool filter sand and the dynamics of water combined in an unforeseen way...

 

Seems to me the reason the plastic bucket brigade reported better results than Shimeks (or whoever it was) is that large rectangular footprints work against establishing an effective nutrient sink by providing a lot of surface area for the oxygenated water flowing over the top of the sand bed to interact with the water within the DSB. To my way of thinking, the strong, more or less unidirectional flow in a rectangular RDSB is essentially a river tank... I've read up on rivers as well as lakes, and when flowing over a coarse bed of gravel or sand, river water flows in and out of the upper substrate in much higher volumes than I would ever have suspected from casual observation. The intuitive assumption that the sand offers so much resistance that any flow within the sandbed will be negligible when the water has a free and unobstructed path on top of the DSB turns out to have no support in the scientific literature -- quite the opposite, in fact. Subsurface currents are much slower than running water, but part of the "river" flowing through a large footprint, rectangular RDSB would flow unseen through the top of the sandbed. Indeed, as I understand it, that was largely the point of using pool filter sand... and I think it worked entirely too well.

 

Hydrodynamic forces -- meaning the current in the upper layer of sand dragging DSB water along with it sort of like the way suction from the water flow from a faucet gets the siphon started for a water change -- slowly but steadily pulled water through those old, large-footprint DSBs and flushed them out, preventing significant accumulation of nutrients in the interstitial water of the DSB's anaerobic zone. Once a new DSB came into chemical equilibrium with the system it was plumbed into, its capacity for nutrient retention largely consisted of the resident population of bacteria and benthic organisms; P and other nutrients that normally build up in the anaerobic zone were instead flushed back into the water column by water circulating through the anaerobic zone. Even N2 gas generated by NO3 reduction in the uppermost anaerobic layer of a DSB readily dissolves back into the water -- I was able to all but eliminate offgassing from a 5" sandbed in a 10G FW hex by inducing a very, very small circulation through it with nothing more than an uplift tube from an old UGF jammed down into the sand in one corner of the tank (...I call it a "ventilated deep sand bed"), so it doesn't take much subsurface flow at all to pull stuff out of a DSB. But if you do that, it's not good for much beyond converting NH3 to NO3. So as a result of circulation within the sandbed, a new large-footprint DSB would only potentially consume detectable amounts of nutrients as it came into equilibrium with the system and cycled, and then it wouldn't do much after that.

 

The problem was the intuitive bias that permitting flow within the DSB itself was necessary to ensure adequate nutrient exchange between the water column and the DSB. The bucket brigade accidentally solved the problem by building DSBs that were tall, narrow, and round, and as a result had poor internal flow even though they were using the same sand. Because of the smaller surface area and less organized surface flow in a bucket DSB, the hydrodynamic pump effect wasn't strong enough to turn over the water in the anaerobic zone. Instead, the plastic bucket DSBs relied on diffusion, not flow, to get nutrients to their lower layers, and the water there turned over very slowly, allowing P accumulation to take its natural course.

 

This theory is consistent with the observation that a large-footprint rectangular remote DSB had to be extra deep to function effectively as a nutrient sink -- to compensate for the coarse medium permitting easy water movement within the sandbed, it had to be deep enough that the bottom of the DSB would be outside the circulation pattern and nutrients could accumulate there in peace. Not sure what to make of the Rubbermaid trash cans, though... I take you at your word that multiple RDSBs had no effect, but if other people are still running theirs, apparently they think they're working. There may be ways to set up the hydrodynamics in round containers to generate slow circulation way down deep in the sandbed and flush them out, or maybe the ones that work are in tall and narrow containers, and the ones that don't are in short, squat containers. Can't work it out farther than that without more data, I think.

 

But, as I pointed out in the other thread, I think a remote deep mud bucket would be an effective P sink. Wouldn't fix the problem, but it would put off the day of reckoning.

 

 

there really is not just one way of keeping a successful reef tank everyone has there own ideas and ways of making it their own tank and thats the point isnt it to have your own part of the ocean in your house

 

Could not agree with that position more strongly, Blackhand.

 

If you have a successful tank, keep doing whatever it is that you're doing -- my job is not to convince you to follow me over the horizon, but simply to report in when I think I've found something interesting.

[MVPaquatics]

In your plan c: soaking the rock. Can you expand on that? Soak in what? How long? Etc?

[Totoro]

Seriously? You think I'm that well organized, MVP?

 

My cunning plan is to remove one piece of LR and change out the half of the sandbed underneath it. Hopefully, while the LR is soaking in FW for what I'm guessing will be a few months to leach out the accumulated P, the new half of the sandbed will be colonized. Then the dead LR goes back into the tank to be brought back to life. When I'm happy with that process, the other piece comes out and the other half of the sandbed gets replaced.

 

This won't get me back to zero, as both the new half of the sandbed and P-free LR will absorb P once they go into the tank... So, best case scenario, I remove half the accumulated P by removing half the substrate, then P equalizes and I remove half of half and get down to 1/4 of whatever level it is that finally prompts me to action. Though, of course, it's a dynamic system, and P will still be accumulating during this process... I figure worst case, I'll end up getting about half of the accumulated P out of the system this way. I'm thinking that would be enough to buy me another couple-three years, maybe more.

[Blackhand]

thanks and im not at all saying you shouldnt be speaking your opinion thats what makes this forum so great everyone sharing their own ideas take a little that and a little of this haha

[pledosophy]

It totally does. A substrate leaching P is generally a recipe for a cyano bloom: http://www.pnwmas.org/forums/showthread.php?31036-Cyano-bactiria&p=300357&viewfull=1#post300357

 

Let it bloom, remove it; repeat until it pulls enough P out of the substrate to lose its competitive advantage and stops blooming.

 

So you want to use cyano instead of algae? Personally I think certain species of macro algae are far more efficient at phosphate/nitrate, and ammonia removal then bacterias can be. The growth rates of racemosa, profliera, or taxifloria are unbelievably fast an ideal circumstances. While cyano can double every 20 minutes in ideal settings, for nutrient uptake it has nothing on algae.

 

Really basic question for you. If cyano would infact grow at a pace where it could be used succsessfully to remove P from a tank, then why is it people have such a hard time getting rid of it? Some people fight it for many months. Some tanks have patches for years. If it were effective at nutrient removal, wouldn't the course of action for cyano be to let it run it's course as it would end very quickly when it consumed the available phosphate?

 

Bioremediation (a cyano scrubber) is my first choice. Failing that, I'll try going with simple chemical equilibrium (a remote deep mud bucket). Plan C is soaking my LR.

 

Your first and second choice involve using bacteria, your third choice involves removing the bacteria you advocate in your second choice. Kind of odd.

 

When you first mentioned soaking your LR, I assumed you were speaking of the process of cooking your rock, where you let it soak in clean salt water to remove stored organic matter. I did not realize you meant to actually kill the rock and start over. I believe cooking the rock which does preserve the life in the rock is a last resort. As for killing liverock, I think it is always a mistake. As the liverock stays in our tank the beneficial bacterias of that rock also multiply which in turn processes more of the waste.

 

No disrespect intended, but the Standard Model says algae is not about addition. It's about ratios.

I am not referencing the Standard Model or Santa Monica's theories. I do not like algae scrubbers personally. I do like algae for nutrient export.

 

The upshot is that the N:P ratio of green algae (especially tropical macroalgae, FYI, which have an average N:P ratio of over 40:1) is higher than the food going into an aquarium (which I'm assuming is 16:1 -- the Redfield ratio -- but may well be enriched in P, what with amino acid supplements and whatever else people are feeding their corals and blending into their fish foods). This means that green algae cannot mitigate P accumulation without supplemental N, and therefore over the long haul, green algae cannot prevent a tank crash due to P saturation. Doesn't matter how much algae you have or how fast it grows. If the N:P ratio of what you're using to export nutrients is higher than the N:P ratio of what's going into the tank to feed the livestock, you're going to be left with surplus P. However it's executed, I believe the concept is, as the title of this thread suggests, fatally flawed -- it's possible run a balanced system with regards to N using green algae, but not P.

 

IME your ratios are a bit off. I guess it would depend heavily on the type and amount of food used. The main food I feed my tank is very low in phosphates with the manufacturer claiming that the max ratio is .o1%. Perhaps this is why in my systems which are filtered by algae I have undetectable phosphate but detectable nitrate. However since there are bacteria in the tank that process nitrate without the need for phosphate, I can see why my nitrates are not sky high, even though I feed what everyone would deem a ridiculous amount a day.

 

Seems to me the reason the plastic bucket brigade reported better results than Shimeks (or whoever it was) is that large rectangular footprints work against establishing an effective nutrient sink by providing a lot of surface area for the oxygenated water flowing over the top of the sand bed to interact with the water within the DSB. To my way of thinking, the strong, more or less unidirectional flow in a rectangular RDSB is essentially a river tank... I've read up on rivers as well as lakes, and when flowing over a coarse bed of gravel or sand, river water flows in and out of the upper substrate in much higher volumes than I would ever have suspected from casual observation. The intuitive assumption that the sand offers so much resistance that any flow within the sandbed will be negligible when the water has a free and unobstructed path on top of the DSB turns out to have no support in the scientific literature -- quite the opposite, in fact. Subsurface currents are much slower than running water, but part of the "river" flowing through a large footprint, rectangular RDSB would flow unseen through the top of the sandbed. Indeed, as I understand it, that was largely the point of using pool filter sand... and I think it worked entirely too well.

 

Lil backwards mate. Shimek claimed far superior results with the bigger footprint. He continues to report the size is needed for bacteria and microfauna production for the bed to be effective longterm. People using the smaller buckets get good results for filtration, but the food production, and creation of a living bed is not achieved.

 

This theory is consistent with the observation that a large-footprint rectangular remote DSB had to be extra deep to function effectively as a nutrient sink -- to compensate for the coarse medium permitting easy water movement within the sandbed, it had to be deep enough that the bottom of the DSB would be outside the circulation pattern and nutrients could accumulate there in peace. Not sure what to make of the Rubbermaid trash cans, though... I take you at your word that multiple RDSBs had no effect, but if other people are still running theirs, apparently they think they're working. There may be ways to set up the hydrodynamics in round containers to generate slow circulation way down deep in the sandbed and flush them out, or maybe the ones that work are in tall and narrow containers, and the ones that don't are in short, squat containers. Can't work it out farther than that without more data, I think.

 

But, as I pointed out in the other thread, I think a remote deep mud bucket would be an effective P sink. Wouldn't fix the problem, but it would put off the day of reckoning.

 

I never ran multiple RDSB's, sorry if that was unclear. I had a single 55g rubbermaid, almost filled to the top with sand and the current moving across the water. I just didn't see much benefit IME.

 

I think part of the way DSB's can sustain longterm is the fauna that grows in them as well. It's not all chemistry, there is some biology in there as well. As for the old tank syndrome, I am really not all that worried. I have seen no evidence that is a real thing, just a theory some people subscribe to. But that is just my opinion.

[Totoro]

Really basic question for you. If cyano would infact grow at a pace where it could be used succsessfully to remove P from a tank' date=' then why is it people have such a hard time getting rid of it? Some people fight it for many months. Some tanks have patches for years.[/quote']

 

The trouble with basic questions is that they appear simple on the surface, but they encompass so many variables and imponderables that a simple answer is difficult...

 

But perhaps the simplest answer is already there in your own words: people fight cyano. It seems unreasonable to complain that there's no anecdotal evidence of cyano being used to effectively export nutrients when the usual response of hobbyists is to do whatever they can to prevent its growth.

 

You're obviously a much more experienced hobbyist than I am -- are you aware of anyone going in the other direction and trying to cultivate cyano so they could physically remove it from the system to export nutrients? I'm not talking about a scrubber, but something simple and obvious like letting it grow in the sump or not pointing a powerhead at a cyano bloom in the DT and trying to make it go away with high flow. Though it may well be impossible to grow enough to make a difference in a reef tank, given the overall high flow conditions... Small organisms like to exploit the boundary layer, which reefers are consciously trying to disrupt.

 

 

If it were effective at nutrient removal' date=' wouldn't the course of action for cyano be to let it run it's course as it would end very quickly when it consumed the available phosphate?[/quote']

 

I'm in uncharted waters. I don't have any good information on how quickly cyano can pull P out of the substrate.

 

My intuition is that something that takes long time to happen will take a long time to undo.

 

 

IME your ratios are a bit off. I guess it would depend heavily on the type and amount of food used. The main food I feed my tank is very low in phosphates with the manufacturer claiming that the max ratio is .o1%.

 

Ah, fair point -- my bias is towards homemade foods. Didn't stop to consider low-P commercial products.

 

But if P accumulation is a problem even with low-P food, then it would seem intuitively obvious that whatever algae is being used to export nutrients must be really, really bad at exporting P...

 

 

Your first and second choice involve using bacteria, your third choice involves removing the bacteria you advocate in your second choice. Kind of odd. ...

 

Lil backwards mate. Shimek claimed far superior results with the bigger footprint. He continues to report the size is needed for bacteria and microfauna production for the bed to be effective longterm. People using the smaller buckets get good results for filtration, but the food production, and creation of a living bed is not achieved. ... I think part of the way DSB's can sustain longterm is the fauna that grows in them as well. It's not all chemistry, there is some biology in there as well.

 

And don't I feel foolish for cobbling together a purely physiochemical model and forgetting that the chief selling point of DSBs is that they provide habitat and food. Been a while since I read up on this stuff, and obviously my bias is showing -- as I said in the other thread, I'm an oceanographer by temperament, not a marine biologist. You're absolutely right: I made the mistake of looking at this entirely through the lens of chemistry. So, let's reconsider in the light of biology...

 

Biologicial sequestration of P dominates in oxygenated DSBs -- that is, the phosphorous is locked up inside living organisms. In anaerobic DSBs, or any anaerobic substrate including the interior of live rock, chemical sequestration of P is the dominant mode.

 

Biological sequestration -- which is the natural bias of a good marine biologist, I totally get that -- may actually interfere with chemical sequestration in a DSB and, overall, hurt more than it helps because benthic fauna stir up the sandbed and keep it oxygenated to a much greater depth than would be the case in their absence. Two pictures are worth a thousand words: http://www.baybenthos.versar.com/benthos.htm

 

Chemical sequestration can store away MUCH more P than biological sequestration in a substrate with a high surface area-to-volume ratio, such as benthic mud or a DSB or even the tiny pores and fractures within LR. This is because PO4, which can persist in anaerobic conditions and will not precipitate out, likes to adhere directly to the surface of minerals.

 

Like everyone else, I feel I have more than enough chemistry to keep track of in oxygenated water, so here's my E-Z conceptual shorthand for anaerobic chemistry: it's Bizarro World. Chemical reactions that we take for granted, like free PO4 and Fe wanting to precipitate out as soon as they hit the water, all run in reverse. In fact, the insoluble precipitates that can be so irksome to us are food for the bacteria in Bizarro World. Orthophosphate, so rare and precious in oxygenated water, is a primary waste product of methanogenic bacteria -- those are the ones at the bottom of the "layer cake" of anaerobic respiration pathways in marine and freshwater sediments:

 

                                        SEAFLOOR
*******************************************************************************************
---- (oxygenated sediment - aerobic respiration) ------------------------------------------
---------------- (nitrate reduction) ---------------- where odorless N2 gas is made -------
--------------- (manganese reduction) -----------------------------------------------------
------------------ (iron reduction) -------------------------------------------------------
----------------- (sulfate reduction) --------------- where super stinky H2S is made ------
---------------- (methane [b]pro[/b]duction) --------------- where odorless CH4 is made ----------

After that, it's methanogenesis all the way down. And also Mn and Fe reducers, but nitrate and sulfate
reducers are restricted to their zones. Note that all zones overlap to some extent, so the upper sulfate
reduction zone overlaps with the lower iron reduction zone, for example, and the lower sulfate reduction
zone overlaps with the methane production layer.

And here's a fun fact to break up the lecture: H2S + CH4 = "swamp gas" -- stinky and flammable!

 

If they're not Fe-limited, the iron reducers will outcompete the sulfur bacteria and methane makers below them for carbon, which is what they're all after. In the real world, between that and the general scarcity of food (organic carbon) on the floor of the open ocean, bacteria in the bottom two layers don't generally see much action unless, like, a whale carcass lands on top of them or something. Closer to shore, bioturbation (critters turning over the mud or sand) tends to stir up the top three layers and allow organic carbon to percolate down to the lower layers. This brings food to the sulfate reducers... Y'know that foul, stinky black gunk in the substrate? Yeah, that smell is H2S from the sulfate reducers -- and if you got sulfate reducers, you got methane producers, which is significant because they're the end of the line...

 

Here's the basic biochemistry of methanogenesis from one of my books:

 

[x CH2O] + [y NH3] + [z H3PO4] = [x CH4] + [x CO2] + [2y NH3] + [2z H3PO4]

 

This is of interest to any fishkeeper because it runs in surplus where NH3 and H3PO4 are concerned -- twice as much comes out as goes in. The extra N and P don't appear by magic; they're in the food the bacteria are eating. See, the bacteria are really mostly interested in organic carbon, which is often the limiting nutrient for them (...and that's why vodka dosing works, incidentally, which I mention not to show off but to demonstrate that this line of thinking is consistent with The Hobby As We Know It -- turns out Bizarro World isn't that bizarre in some ways), and all the stuff that's attached to the carbon is kind of in their way.

 

Crucially, the chemistry of methanogenesis shows that in Bizarro World, biological sequestration doesn't work -- it cannot work. The limiting nutrient for the anaerobic bacterial community in the substrate is carbon, so nitrogen and phosphorous are in surplus. N and P don't end up locked away inside anaerobic bacteria, they're unwanted waste products, like oxygen is unwanted waste for plants. The N is soluble in oxygenated water and can diffuse out of the substrate to be captured by autotrophs, but the P is stuck.

 

The flipside of this is that chemical sequestration doesn't work in oxygenated sediments. So in oxygenated DSBs, P storage is essentially a function of overall biomass.

 

In anaerobic conditions, not only is P stored efficiently in the substrate, but the bacteria are actively putting it there. This is the basic mechanism of P accumulation -- it's driven by C-limited anaerobic bacteria, but the reason P actually accumulates is chemical sequestration. It's P sticking to the mineral surfaces atom by atom. Well, really it's PO4... but then, there's just the one atom of P in each ion, so... okay, I'm sticking with "atom by atom", and the purists can just call it poetic license.

 

Anyway, that's why I think a remote deep mud bucket would work -- simple chemical equilibrium should eventually diffuse enough P into the anaerobic mud to export a useful amount. Bacteria can only speed up the process.

 

So... When you say "buckets get good results for filtration", pledosophy, that's unclear to me, and as you might imagine, I'm curious... Exactly what do you mean by "good results for filtration"? Is that NH3 --> NO2 --> NO3 type filtration, or general nutrient (including P) removal?

 

 

I am not referencing the Standard Model or Santa Monica's theories.

 

Yeah, I know. This is all kind of OT. I'm not impressed by SantaMonica's thinking, myself, and I'd really rather be defending the Standard Model than trying to untangle a pile of anecdotal information about deep sand beds on the fly, but then again, there doesn't seem to be much discussion of anaerobic environments in the hobby, so maybe this will be helpful.

 

The way I like to look at it, last year my big epiphany was about bacterioplankton, so I was about 35 or 40 years behind the real oceanographers. This year, it's P ratios, which puts me about 25 or 30 years behind -- so I'm totally catching up!

 

 

As for the old tank syndrome' date=' I am really not all that worried. I have seen no evidence that is a real thing[/quote']

 

And you wouldn't, if you chemically scrub your system to control P.

 

But if you're truly able to maintain a reef tank over the long haul using nothing more than green algae to export P, you're my hero. Even if you're using low-P commercial food, I'm impressed. Do you have any write-ups of your tank management practices online? This deserves close study, as I'm all too aware that what I'm doing isn't a viable approach to the P problem.

[Jeramy]

If you or any one for that mater could clarify for me the diffrence between Phosphorus Phosphate when you initially brought up "P" i thought you were talking about phosphate. I think it would help me better understand what I am reading up above if I knew the diffrence and their relationship. Thanks =)

[Totoro]

Don't stress too much over it. When talking about nutrient cycling in broad terms, there's often not much need to differentiate between different forms of the nutrients involved because they routinely switch back and forth between them. Even scientists write about N and P, so you get sentences like this:

 

"A classic example of the mechanisms of inertia is formed by the P release from sediments; in pristine systems, sediments act as a sink for P, but on increasing eutrophication the ability of sediments to capture P often decreases." (from N:P Ratios in Estimating Nutrient Limitation in Aquatic Systems by Petri Ekholm, 2008)

 

But here's the little science lecture, if you're interested...

 

P is the symbol for the chemical element phosphorous.

 

Orthophosphate = phosphate = PO4 = one atom of phosphorous and four atoms of oxygen

 

PO4 is actually an ion; the complete molecule is phosphoric acid: H3PO4

 

H3PO4 breaks up in water to 3 H+ ions and the negatively charged PO4 ion.

 

PO4 is highly reactive and wants to precipitate out of oxygenated seawater (edit for FW aquarists: and also hard FW) at the drop of a hat. PO4 is sometimes called inorganic or mineralized phosphorous. It's the only form of P useful to plants, including algae, so the fact that there's not much around makes it the most common limiting nutrient for autotrophs.

 

Considerably less than 5% of total P in natural waters is PO4; in surface waters where photosynthesis takes place, PO4 is likely less than 1% of total P. The rest is organic P -- ie, P that has been consumed and incorporated into biological molecules like amino acids and proteins.

 

Most organic P in the water column is biologically sequestered inside plankton and fish and other organisms. I don't have numbers for the marine ecosystem, but in FW lakes, 70% of organic P is biologically sequestered in the trophogenic zone (...the upper levels of a lake where primary production and life in general happens). In surface waters where photosynthesis takes place, over 95% of total P may be biologically sequestered. The remaining organic P is either dissolved or in colloids, a sort of intermediate phase between being dissolved and being particulate matter. An individual atom of P may change between these four forms -- free range orthophosphate, colloidal phosphorous, dissolved organic phosphorous, and biologically sequestered organic phosphorous -- either through biological activity (like being consumed by algae or excreted by bacteria) or physiochemical processes (which can shift P between dissolved organic P, colloidal P, and orthophosphate).

 

Does that make it better or worse?

[Jeramy]

No that actually helped thank you =) So if PO4 is only 5% or less of the total P in the water then our Phosphate test kits are only showing a fraction of the total problem? Also how would one test the consentrations of P in the sand bed? How would you know if it was building up to unexceptable levels? Also as it gets more concentrated in the sand bed and starts to leach out would you not be able then to remove it from the system throu one of the multiple choices for nutriant export? ALso the organic P be able to be able to be removed by our protien skimmers? Thanks for this disscusion I have learned a lot so far =)

[Totoro]

So if PO4 is only 5% or less of the total P in the water then our Phosphate test kits are only showing a fraction of the total problem?

 

Test kits are showing only a fraction of total P in the system, yes, but they're showing the most important fraction. I have a recollection of seeing mention in online forums of test kits that can apparently measure organic P as well as PO4, but IIRC best practice in a laboratory setting is to convert all organic P to PO4 and then measure that -- and in any case, I can't see that measuring total P or organic P would be at all useful to aquarists.

 

PO4 concentration in the water reflects the overall P level because, broadly speaking, the water column is in chemical equilibrium with the substrate and PO4 is in equilibrium with the other, non-detectable states that P can exist in. In principle, PO4 is even in equilibrium with biologically sequestered P over the medium to long term, as the organisms sequestering P will eventually die and release their stored P during decomposition. Biologically sequestered P can turn over very quickly in the case of small organisms like algae and bacteria -- sometimes in a matter of hours -- or much more slowly, potentially taking years or even decades in the case of fish and other large organisms. Realistically, though, hobbyists diligently remove dead livestock from their tanks, which of course exports the P (and N and S and everything else) they contain.

 

It's important to note that "equilibrium" doesn't mean that P in the water is equal or close to P in the substrate. Phosphate concentrates in anaerobic areas because it can remain soluble there (the solubility of calcium phosphate, which in its several different forms is collectively the most common PO4 precipitate in SW, is governed by pH, and anaerobic water is generally somewhat acidic -- which would explain why aragonite and white sand DSBs are prone to noticeable shrinkage over time, it crosses my mind). In the overlying water column, PO4 wants to precipitate out -- which, BTW, is why the entire system doesn't crash from skyrocketing P when you mess around with your substrate: hiding in the cloud of fines and detritus that gets stirred up is a cloud of P precipitates. Thus, the natural equilibrium is a whole lot of PO4 in the substrate and a little bit in the water, so by the time PO4 rises to detectable levels in the water, there’s already a substantial accumulation in the substrate.

 

 

Also as it gets more concentrated in the sand bed and starts to leach out would you not be able then to remove it from the system throu one of the multiple choices for nutriant export?

 

Yes. That's how P is managed with chemical scrubbing -- removing P from the water pulls more out of the substrate to maintain equilibrium. This brings down the overall level of P in the system, but hobbyists will stop scrubbing when they reach an equilibrium between the water column and the substrate that puts an acceptably low level of PO4 in the water. And then, of course, P begins to accumulate again...

 

Which is one of the reasons I don't like chemical P mitigation -- it's a treadmill you can't get off of.

 

 

ALso the organic P be able to be able to be removed by our protien skimmers?

 

To some extent, yes. Bacteria and organic matter removed by skimming carry away the P sequestered therein, but obviously this isn't enough to mitigate the problem or skimmed systems wouldn't show P accumulation.