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Thread: Scrubbers DO NOT export Phosphorus

  1. #41

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    Quote Originally Posted by Garf View Post
    Gonna throw a spanner in the works here. The 8% excreted P (linked earlier) is not of total biomass, it's of P. UPTAKE. So the remaining 92% is translated to growth or storage, hence removed when harvested.
    Actually you may be onto something here!...let me take a closer look. And to make matters more confusing, it is actually the bacterial biomass that it is being compared to

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

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

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

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

  2. #42

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




    Correct. But organic P will lead to more Pi, you just may not be able to measure that uptick in Pi because it is consumed so quickly. If there is enough Pi to feed good algae growth, then some of that Pi could also be inhibiting coral calcification.
    no there is an equilibrium in the water if pi is released and gets bound to a coral skeleton it will come off into the water column as the water phosphate is lowered

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

    .03 and .00 phosphate is common.

  3. #43

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    Quote Originally Posted by kotlec View Post
    There is very big mathematical or logical error in this calculation. Most likely both.
    I see I was not the only one that thought it didn't make sense.

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

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

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

  4. #44

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

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

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

  5. #45

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    Very well said, thank you!

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

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

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

  6. #46

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    Quote Originally Posted by Skinnysloth View Post
    I see I was not the only one that thought it didn't make sense.



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

    We may achieve an equilibrium with the rate of phosphate introduction via food and export/sequestration via ATS, skimmer, GFO, sand, rock, etc., but I still don’t understand how the ATS is not exporting P when you harvest it. Let’s say that P is continually recycled during the Calvin cycle, so the P is neither gained nor lost. Even with the leakage of 8%, if the algae is able to grow faster than the 8% loss, are we not taking additional P from the water to power the Calvin cycle in the new algae growth/cells and getting rid of P when we harvest?
    Yes my analogies were a little misguided. As Garf pointed out, those studies compared algae Po excretion to bacterial biomass, NOT to algae biomass. But the revolving door analogy I think is still with merit. It is the quantity of P flux that is still a mystery. As Amphiprion just stated, that is something that may be insignificant in reality.

  7. #47

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

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

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

  8. #48

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    Quote Originally Posted by Nick28 View Post
    If this were true, the lowest possible amount of P in a tank on average would continue to rise as years went by (creating a floor that rises) and you would have use another type of filtration or water change to bring it down.
    I don't quite understand what you're getting at.

    organic p ends up as inorganic p at some point so it would have to show
    Not necessarily, organic P can settle as detritus or become locked up in calcium.

    I don't agree with it , but i'm willing to be proven wrong.
    Instead of looking to be proven wrong, how about finding evidence that will prove you right?

  9. #49

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    Quote Originally Posted by xerophyte_nyc View Post
    I don't quite understand what you're getting at.
    If p became an issue it would show in the water column

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

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

  10. #50

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    Quote Originally Posted by Nick28 View Post
    If p became an issue it would show in the water column
    Do you mean with testing?

    detritus is food it does not stay detritus, old detritus totally changes form and new detritus gets created
    Well in the ocean, this is not the case. But in our aquariums, this could be more or less true.

    Rock and sand will leach p untill exhaustion.
    pH has to drop into the 7's for this to happen.

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

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

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