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Thread: Scrubbers DO NOT export Phosphorus

  1. #21

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    Quote Originally Posted by xerophyte_nyc View Post

    I have a completely unproven theory that a scrubber selects for specific bacteria that attach to the screen, like how GHA seems to dominate. This bacteria grows together with GHA and forms part of 3d matrix. Within the bacterial biofilm, there is efficient nutrient transfer going on locally. Po to Pi to Po, right on the screen. Some Po escapes and goes to the tank. When I dip my scrubber screen into my tank to let pods escape, I notice an oily residue that washes away. Is this detritus that is decomposing? Is it part of a bacterial biofilm?
    there is also N released by this residue and it has an acceptable N:P ratio for later reabsorption after cleaning. You also don't want N and P to be absolutely zero which is impossible anyways.

  2. #22

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    Quote Originally Posted by Nick28 View Post
    i never found a DSB to be a phosphate sink its constantly moving like gears on a machine problems arise when there is no anaerobic region do to too much flow or too shallow (too much oxygenation).
    A functional DSB with good circulation and movement of pore volume should in theory work very well. Also, depending on the size of the DSB and other export methods being used, a DSB could be sinking in P for many, many years until there is trouble. The problem is there is no good way to quantify this process in our hobby.


    faster at a lower ph and at deeper levels, however there is biological activity occuring on the surface of every grain of sand there are acidic enzymes and carbonic acid released from bacterial respiration ,plus fish waste releases acids that must be neutralized anyone who has had an aquarium for years will eventually need to add aragonite sand as it dissolves grains get finer.
    Correct. This is happening on a small scale, every minute, every hour. I don't know exactly how this contributes to the overall P, in relation to the dissolved portion already present via other biologic activities.


    If P ever did become a problem say from an unclean water source you could use calcium carbonate or calcite in a media bag like GFO it wont be as effective but will be cheaper
    If the unclean water source has Po, then GFO will do nothing, but a calcium bag would help - how much, I don't know. Calcium and GFO are binding different forms of P.

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


    the scrubber can process nitrogen, basically setting up an empty tank with nutrients and a scrubber will yield the same effect as a tank with rock and sand if this is a problem the P would have no where to settle or bind, it would accumulate in the water column and cause algae or cyano problems in the display tank that are unsolvable by the ATS alone.
    The ATS is out-competing the nuisance algae for Pi. The excess P in the tank is in organic form. If there are not enough bacteria to consume it, or if carbon is limiting (which it will be at some point, why do ATS tanks trend to alkalinity?), then the excess is deposited as detritus. If carbon is not limiting (let's say you dose vodka or CO2) then bacteria will be able to process all that Po but there will be a massive bacterial bloom. Since in most ATS tanks carbon can be a limiter, it means that some Po is leftover.

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

    The ocean is not an aquarium
    Absolutely. I eluded to this in one of my earlier posts. We have to be careful when extrapolating marine science to our aquaria. Unfortunately, hobby literature is lacking so sometimes all we have is marine research.




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

  3. #23

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    Quote Originally Posted by celtic_fox View Post
    Seems like some assumptions in there just to try and win an argument. (I'm not saying you aren't or won't eventually be proven right. I'm just saying you're making some assumptions that don't necessarily happen.) We do see people with less growth when they feed less, and more when they feed more. Sometimes it happens right away, sometimes it takes a cycle or two for the effect to become apparent.
    I really am not trying to prove anything, this is not about starting or winning an argument. My only vested interest, as with everyone else, is to come up with strategies to make our tanks beautiful with preferably less labor. I feel that when I invested time and energy into researching an ATS and how it helps a tank, there wasn't full disclosure.

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

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

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

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



    Also, can you re-explain this? (Seriously, I'm missing something in your statement. And just for the record, I'll be the first to admit, I don't understand all of this, so this is a straight question, not an argument.) If bacteria is utilizing the high levels of dissolved Po in favor of the calcium-bound Po, then where is the "excess Po" that you're refering to coming from? (Are you saying the calcium-bound Po is floating around?)
    It can get confusing. It took me time to grasp it. The excess Po exists because there is not enough bacterial biomass to get to all of the Po in the water column. Some of it will precipitate as detritus. It is not much on a day to day basis. But it will build up in time. That's why skimming, water changes, etc. are helpful - they remove the dissolved Po. It is competition with bacteria. If you compete well, bacteria population dwindles, they make less Pi (so less food for algae), and they can start to use some of that calcium-bound P. It all comes down to understanding and manipulating bacteria. They are in control.

    Here are some links for further "enrichment":

    Phosphate Cycle image, with means of export

    Adsorption of phosphate on calcium carbonate

    Thread on reef central with Randy Holmes Farley discussing phosphate and calcium

    Excretion of Dissolved Organic Phosphorus in Tropical Brackish Waters - this one shows the 8% Po excretion per 2-4 hrs

  4. #24

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

    Quote Originally Posted by xerophyte_nyc View Post

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

    In essence, an ATS is a Po doser. What I am looking to find out is where is the sweet spot, at what point do the negatives outweigh the positives. It is far more effective to remove Po right away (skimmer, frequent water change, remove detritus) before it ever gets to the bacteria. Algae is the last one to get the P. That is inefficient.
    Scrubbers don't lower alkalinity (minimal effect at best) high calcification rates do, (and this tends to happen on tanks run with scrubbers) bicarbonate is absorbed, HO- is released this hits the surface and binds with CO2 to form a new bicarbonate ion.

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

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

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

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

    phyto, zooplankton, coral and fish are organic P






    Interesting analogy
    thanks

  5. #25
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    My head doth explodeth

  6. #26

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    Quote Originally Posted by Nick28 View Post
    keep in mind i'm not being belligerent with my posts
    I know. No worries, even if someone does get upset. I understand.


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

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

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

    organic p is harmless it wont be a problem until things start dieing (say a power outage) and you will get inorganic p relatively quickly
    organic P by itself is harmless, correct. But it doesn't just float around. Not all of it is consumed. Some will become detritus or bound to substrate. That is the bad part - we can't measure this. If the substrate fills up and there are no more binding spots, we have ourselves a problem. This could take many years depending on other variables. Or maybe not.

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

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

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

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

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

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

  7. #27

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    Quote Originally Posted by Floyd R Turbo View Post
    My head doth explodeth
    Happened to me too. Once your neurons settle in, it will get better.

  8. #28
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    Way to many unscientific 'assumptions' in this thread and we all know what 'assuming' leads to. If you do A then that can equal B, C, or D, but if you do B, then A and C are the outcomes, but if you do D... etc etc... bottom line, way to many variables to make any type of conclusion. One of my tanks (the one doing good and only ran an ATS since day 1) goes against pretty much everything that has been said in this thread in regards to bacteria, skimmers, PO4 not being exported, etc, which makes me not believe any of the 'facts' being stated in this thread.

  9. #29

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    Quote Originally Posted by xerophyte_nyc View Post
    When the ATS is harvested, the net P removed at that moment is less than the net P that was imported during that entire week of growth. Check the reference below. The researchers discovered that on average 8% of algae's P biomass is excreted during a 2-4 hour period of a light cycle, and this was at low nutrient levels where growth is slower. Using those values, if your ATS is lit 12 hours, 25-50% of the algae P biomass is excreted per day. In 2-4 days, the net export is equal to net import. After a week???
    Help me understand this statement. I may be missing something. So if 8% of the algae's P biomass is excreted during 2-4 hours of a light cycle, then in 2-4 days it would have excreted 100% of its biomass. So at this point, you're saying the amount of P that went into the algae had all been excreted. Does the algae just stop uptaking P, while excreting 8% every 2-4 hours. In the 2-4 hour period, it 'sequestered' 92% and is that all the P that it ever needs without uptaking any more additional P? What maybe confusing me is, I don't know what % of the biomass is taken up in the form of P during that 2-4 hours. If the algae intakes 10% of its biomass in P and then excretes 18%, there would be a net loss of 8% of P from the algae, but by that account, the algae is just dumping P into the system.

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

    Great topic and discussion by the way.

  10. #30

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

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

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