Biopellets causing Acropora to STN/RTN?

[Reefin' Dude]

found the full article for the link i posted before that is of most relevance to what we are talking about.

I. Project title: THE ROLE OF SUSPENDED CALCIUM CARBONATE IN THE PHOSPHORUS CYCLE IN FLORIDA BAY

G~

 

[jda]

My understanding is that if one has consistently low phosphate levels, and steady pH, one is unlikely to experience much in the way of phosphate leaching back into the water. Is this incorrect?

You are right, but not for the reasons that you might think.

What appears to be leeching of the phosphates is actually that the sand bed is incapable of doing it's job anymore by bonding and processing, so levels rise. The sand is "full." ...so not true leeching, but P levels will rise since they go unprocessed.

This surprises reefers who have had success for years of doing nothing to their sand. They are used to having no/little N and P, so they start with the assumption that it is not them - which makes sense since they have never/rarely "seen" it. At first incapable of realizing that they have always had it and not knowing that the sand has been taking care of the P, they assume that the sand much be "leeching" since it worked before. Some will get it when you explain the process, but some will not and blame the sand forever.

A properly maintained sand bed will continue to process and bond, which appears to "not be leeching."

In the end, it all gets back to proper routine maintenance, not a low presence of phosphate... but the low presence of phosphate is a product of the maintenance. ...so I guess that it is the same, but not really, but kinda, but kinda-not... IMO.

I am just a In Home Reefer Scientist, not a real Scientist and I did not even stay at a Holiday Inn Express last night, so... this is opinion is likely not worth the cost of the byes that it is stored in.

 

[hart24601]

People tend to make it sound more difficult and complex than it is.

Most SPS require stable water chemistry, adequate water movement, adequate light, adequate nutrition, and reasonably clean water.

IME, many SPS corals are among the most hardy, least picky, and most bulletproof once established. My bird's nest is easily the fastest growing of my long term residents. Yesterday, I accidentally broke about 8 tips off of branches, and it had already grown back over and rounded off the broken edges by lights out tonight.

Most montis seem pretty indestructible. I have an M. mollis that was knocked onto a Galaxea when it was ~half dollar sized a few months ago. About 5 sq millimeters of tissue survived. Now, it is larger than it was when the incident occurred.

My Hydnophora is the only SPS I have that seems a bit finicky and slow growing. I recently moved it to a higher flow area, so we'll see if it's happier there.

Euphyllia are the corals that I can't keep happy for the life of me, and my Symphyllia is also pretty slow growing and touchy.

For whatever reason, my SPS always seem to be less offended by "minor" WQ issues, like application of aiptasia killing gunk near them, or a few hours with no flow, or a few days without 2 part, etc.

+1 While I have had trouble with some SPS most of them outgrow my other corals tenfold. My SPS have also been very tough, most my leathers died but not the SPS. Some of the nicest reef tanks you will ever see don't have anything fancy, just a few water changes. I have SPS of all types out growing my biocube for quite a long time now and that tank only gets serviced about once a month.

All these problems with calcium based rocks. Just use ceramic based live rock and substrate if desired.

 

[dkeller_nc]

What appears to be leeching of the phosphates is actually that the sand bed is incapable of doing it's job anymore by bonding and processing, so levels rise. The sand is "full." ...so not true leeching, but P levels will rise since they go unprocessed.

This is actually not quite correct from the standpoint of the physical chemistry of the water and solid substrates. What is actually occurring is that at high phosphate concentrations in the water, calcium phosphate will precipitate on solid surfaces, including the aragonite in reef sand and live rock. However, this precipitation isn't irreversible, and the partition coefficient for calcium phosphate between the tank water and the aragonite substrate isn't all that high compared to something like ferric hydroxide (GFO). So when the tank water concentration is low, any calcium phosphate that's precipitated in the sand bed and on the rocks will re-dissolve.

So in this sense, it isn't possible to "fill up" a sand bed with phosphate unless the tank water concentrations remain quite high - well in excess of 1-2 ppm, which would be considered excessive by most SPS tank keepers.

This same principle applies to the binding of phosphate to ferric hydroxide - it's technically true that phosphate can leach back into seawater from the absorbed form on the GFO particles. But the partition coefficient is so incredibly high for ferrous phosphate that the water's phosphate concentration in equilibrium with ferric hydroxide is essentially zero.

 

[Reefin' Dude]

where do you get the 1-2ppm from? in the study i linked to earlier clearly shows that phosphate absorption on calcium carbonate occurs at 2mM levels, until equilibrium is attained. this equates to about 0.187ppm PO4 in Salt water. how is that anywhere near 1-2ppm?

is it an equilibrium reaction or not. if it is, and it seems like it is from the study shown above, than why would it not be an equilibrium reaction all the way down to normal NSW levels of PO4, 0.005ppm at the minimum?

do you have the partition coefficient of calcium carbonate and ferric hydroxide?

G~

 

[dkeller_nc]

If you mean the "Role of Suspended Calcium Carbonate in The Phosphorus Cycle of Florida Bay", the authors used:

5 mmol in 500 ml Phosphate for the adsorption kinetic studies, which equates to 950 ppm.

For the desorption kinetic studies, they saturated 2 grams of calcium carbonate with a 110 mmol phosphate solution, which equates to 10,450 ppm.

For the adsorption equilibrium studies, they used solutions ranging from 1 mM to 60mM, which equates to 95 ppm to 5,700 ppm.

In other words, they were doing their tests in concentrations of phosphate that vastly exceed what we would (hopefully) encounter in a reef tank, and the concentrations of ions in solution sensitively affect the partitioning (and % saturation) of these ions between precipitated and solution forms.

 

[Reefin' Dude]

we know that calcium carbonate is a phosphate binder. that can not be disputed.

i think our disagreement is in how much P it can bind and what "equilibrium" means.

in this study:

Calcium Carbonate Phosphate Binding Ion Exchange Filtration and Accelerated Denitrification Improve Public Health Standards and Combat Eutrophication in Aquatic Ecosystems

"Sump water and water throughout the marsh, especially in the northwest corner, have average phosphate concentration of 2.34 ppm (7.51 × 10−6 mol/L)."

"The amount of calcium carbonate needed to decrease phosphate, as determined from the reaction calculation, by a certain amount in a certain amount of water was calculated to be 4.78 × 10−4 moles per liter per ppm phosphate, as follows:

(CaCO3)=Kcp([PO43−])(V),
(4)
where Kcp = 4:78 × 10−4 moles per liter per ppm phosphate For CaCO3 in milligrams, Kcp = 48:7 The data from the calcium carbonate reaction mechanism analysis lead directly to the calcium carbonate lacing procedure. A phosphate level of 0.75 ppm was desired for testing purposes, and the results were very accurate. The average phosphate levels after the addition of calcium carbonate came to a statistically significant (p < 0.001) 0.74 ppm (Figure 5), which is well within the statistically significant range (p < 0.01)."

is not that volume of calcium carbonate they used far less than the amount of calcium carbonate we have in our systems with just regular live rock, not to mention any substrate that may be used? as long as the calcium carbonate media in our systems has less P than the water column, and greater than the formula listed above there will be P binding going on correct?

the data for the other water volumes is even better for the use of calcium carbonate as a phosphate binder.

G~

 

[jda]

In the "JDA's Reefs Since 1992 Study" calcium carbonate can bind enough phosphates so that since a Salifert Test kit was introduced for Phosphate, there have never been any detectable results with no fuge, GFO (like they had it back then) or carbon dosing. I am pretty sure that it can keep an equilibrium of near zero - obviously I have enough to keep the SPS growing and even some hair or other algae if my CUC is not on their game. Is this science, or what?

I am not sure which study is saying what, but in a typical tank, I think that aragonite does just fine keeping the phosphates more than manageable.

 

[dkeller_nc]

as long as the calcium carbonate media in our systems has less P than the water column, and greater than the formula listed above there will be P binding going on correct?
G~

Yes, and the calcium carbonate in the system will desorb phosphate just as rapidly when the water column is low in phosphate.

So in that sense one cannot irreversibly "fill up" the sand bed or LR in an aquarium with phosphate. You can keep a very high phosphate input to the tank with no other substantive means of removal and both "saturate" the substrate and water column with phosphate. But as soon as you lower the water concentration of phosphate by protein skimming, water changes, and/or use of GFO and other phosphate absorbers, the sand bed will give up that bound phosphate.

That will, of course, affect how fast the phosphate concentrations in the water column will come down upon the implementation of phosphate absorption/dilution strategies, but the ultimate end point is the same.

 

[jda]

Is this something that you are supposing based on literature and studies, or based on your own experiences? I am not doubting or anything, just looking to qualify. I have not found the same thing with my own experiences, so I am looking to learn and perhaps restudy.

I have not have the same experiences firsthand. I can have tank water levels of P that are undetectable (on salifert), but if I remove some of the sand from places in my tank and melt it in some CO2 water for a few days, the phosphates test fairly high at around .25 to .30 in aggregate. Anecdotally, the more "maintained" places in the sand are around .10 and the less "maintained" around .50. I am sure that if I dissolved more, then levels would further elevate. I have personally found that the sand bed does not give up the bound phosphate when the water levels are low.

I suppose that my hypothesis is wrong and the sand could be giving up P in low tank level conditions. However, if it is, then what is happening to it? I don't use GFO, dose carbon to consume it?

 

[Allmost]

anything used too much, will cause STN / RTN..

even if you fart by your skimmer too much, your corals will STN !

but farts are not a big STN factor.

 

[jda]

You might be onto something there... methane reactor to feed into the skimmer pump for better organic bonding.

 

[Reefin' Dude]

Yes, and the calcium carbonate in the system will desorb phosphate just as rapidly when the water column is low in phosphate.

So in that sense one cannot irreversibly "fill up" the sand bed or LR in an aquarium with phosphate. You can keep a very high phosphate input to the tank with no other substantive means of removal and both "saturate" the substrate and water column with phosphate. But as soon as you lower the water concentration of phosphate by protein skimming, water changes, and/or use of GFO and other phosphate absorbers, the sand bed will give up that bound phosphate.

That will, of course, affect how fast the phosphate concentrations in the water column will come down upon the implementation of phosphate absorption/dilution strategies, but the ultimate end point is the same.

if phosphates behave equilibrium like you say, then yes you are correct for the calcium carbonate in direct contact with the open water column. unfortunately (or fortunately depending on which side of the poo as a pet camp you are on) the substrate itself is an ever increasing permeable barrier to the equalization. this along with the fact that as detritus is worked down into the substrate the amount of P in direct contact with the calcium carbonate goes up, which in turn increases the amount of P that can bind to the calcium carbonate until all binding sites are full. luckily for those that use a substrate all of that bacterial activity and worms help in the slow migration of this slow increasing level of P.

of course we know that this is occurring because of the life that is in the substrate. if the P was not there to feed the organisms, than they would not be there. how much poo does one want to keep as a pet.

if one were to mix the substrate layers and the more P laden calcium carbonate were now up on top, than there would be a release of P from the calcium carbonate into the open water column if P reaches equilibrium with the calcium carbonate and the open water column.

substrates acts as P sinks.

G~

 

[dkeller_nc]

substrates acts as P sinks.

G~

Yes, in the sense that they can act as a dynamic reservoir for phosphate in a high PO4 environment. But the problem is - so does the live rock, or any other calcium carbonate in the system. In this sense, it is highly illogical to declare that substrates are ultimately damaging to the maintenance of a reef tank, but live rock isn't (neither of them are harmful).

 

[dkeller_nc]

Is this something that you are supposing based on literature and studies, or based on your own experiences?

An understanding of physical chemistry, actually. But also my own experiences and literature.

From the standpoint of your observations, there may well be a perfectly logical alternative explanation. When you dissolve a solid substrate in an acid and test the ionic composition of the dissolved liquid, you get a total picture of the average composition of the solid material.

But in general, that doesn't mean it acquired that composition in one's reef tank, in fact it's highly unlikely that it did so. What is considerably more probable based on the mass balance is that the outcome of such testing gives insight into the composition of the material when it went into the reef tank.

 

[Reefin' Dude]

Yes, in the sense that they can act as a dynamic reservoir for phosphate in a high PO4 environment. But the problem is - so does the live rock, or any other calcium carbonate in the system. In this sense, it is highly illogical to declare that substrates are ultimately damaging to the maintenance of a reef tank, but live rock isn't (neither of them are harmful).

LR can be in the open water with flow all around it. it is able to self clean, which a substrate is not able to do.

a substrate is more likely to be harmful, while LR could not be. this is especially true if one treats the substrate in the manner most recommended. do not touch it. if LR is not exposed to enough flow all around it, then yes, you are right it can become as much of a P sink as a substrate. a substrate is always going to be a P sink. the only way to keep it from being so is if it is siphoned cleaned or replaced on a regular basis to remove all of the detritus from it. as long as there is detritus in the substrate, than the calcium carbonate around the detritus is going to have an elevated P level than the calcium carbonate not in direct contact with detritus or other waste products.

G~

 

[Reefin' Dude]

An understanding of physical chemistry, actually. But also my own experiences and literature.

From the standpoint of your observations, there may well be a perfectly logical alternative explanation. When you dissolve a solid substrate in an acid and test the ionic composition of the dissolved liquid, you get a total picture of the average composition of the solid material.

But in general, that doesn't mean it acquired that composition in one's reef tank, in fact it's highly unlikely that it did so. What is considerably more probable based on the mass balance is that the outcome of such testing gives insight into the composition of the material when it went into the reef tank.

could it be the fact that the calcium carbonate in the substrate has been exposed to detritus all around it? detritus has a high P content. if calcium carbonate is an equilibrium reaction, and a substrate is a semi-permeable barrier, than as one goes deeper in the substrate, the more P there is going to be. if there is more P, than there is more P on the calcium carbonate to reach equilibrium, correct? not sure how this does not make sense.

G~

 

[dkeller_nc]

this along with the fact that as detritus is worked down into the substrate the amount of P in direct contact with the calcium carbonate goes up, which in turn increases the amount of P that can bind to the calcium carbonate until all binding sites are full.

how much poo does one want to keep as a pet.

if one were to mix the substrate layers and the more P laden calcium carbonate were now up on top, than there would be a release of P from the calcium carbonate into the open water column if P reaches equilibrium with the calcium carbonate and the open water column.

A couple of final thoughts, and then I'm going to bow out of this discussion since the argumentation has been reasonably well discussed.

First, it is generally incorrect to think in terms of "direct contact" in the context of liquid-solid system. There is always a significant liquid interface between particles in any packed bed, whether it's a sand bed in an aquarium or media in a reactor. Reactions and adsorption/desorption proceed by physical mechanisms of diffusion through this boundary layer of liquid.

Moreover, in aqueous systems this diffusion between the bulk liquid and the particles is extremely quick - on the order of 1 or 2 seconds. It is true that one can establish a gradient between the bulk liquid and some point down into the packed bed, but this is a dynamic gradient caused by continuous physical and biochemical processes that are continually consuming or giving up chemical compounds. That's why it's possible to develop anoxic conditions within a sand bed.

But, no matter one's preferences, it is fundamentally incorrect to think of a sand bed (or any packed bed or substrate such as LR) as a reservoir of binding sites for phosphate that can be irreversibly filled up. There is always an exchange between the bulk liquid and solid material, and if one or the other is "deficient" in phosphate, then phosphate will transport to that phase. This is fundamental to chemistry and physics, and is sometimes referred to colloquially as "nature abhors a vacuum".

If this were not true, then the sand, live rock, and any other solid calcium carbonate in the ocean would be completely and irrevocably saturated with calcium phosphate. And it would be utterly impossible to leach this phosphate back out of the sand or rock as is commonly and repeatably done by hobbyists.

 

[Reefin' Dude]

A couple of final thoughts, and then I'm going to bow out of this discussion since the argumentation has been reasonably well discussed.

understood, but it seems like there is still a good amount of discussion left.

First, it is generally incorrect to think in terms of "direct contact" in the context of liquid-solid system. There is always a significant liquid interface between particles in any packed bed, whether it's a sand bed in an aquarium or media in a reactor. Reactions and adsorption/desorption proceed by physical mechanisms of diffusion through this boundary layer of liquid.

Moreover, in aqueous systems this diffusion between the bulk liquid and the particles is extremely quick - on the order of 1 or 2 seconds. It is true that one can establish a gradient between the bulk liquid and some point down into the packed bed, but this is a dynamic gradient caused by continuous physical and biochemical processes that are continually consuming or giving up chemical compounds. That's why it's possible to develop anoxic conditions within a sand bed.

wouldn't the existence of an anoxic condition indicate that there is not an extremely quick diffusion between all of the layers? if the anoxic layer is just a few cm below the surface, than why wouldn't a solid like P also be increasing if a gas such as O2 could not diffuse quick enough between the water surface interface to maintain constant levels within seconds? something is not making sense? either there can be adequate diffusion to maintain equilibrium, or there can not be. wouldn't a gas have a higher affinity to maintain equilibrium, than a solid?

But, no matter one's preferences, it is fundamentally incorrect to think of a sand bed (or any packed bed or substrate such as LR) as a reservoir of binding sites for phosphate that can be irreversibly filled up. There is always an exchange between the bulk liquid and solid material, and if one or the other is "deficient" in phosphate, then phosphate will transport to that phase. This is fundamental to chemistry and physics, and is sometimes referred to colloquially as "nature abhors a vacuum".

you are correct if there is sufficient movement of media to allow for the equalization of P between the solid calcium carbonate and the liquid media. the problem is that we are not only dealing with P in the water, we are dealing with the P from detritus. it is this P that is causing the increase in P of the calcium carbonate media that is around the detritus. if detritus did not accumulate in our systems, than we would not have to worry about our systems increasing in P over time. if one were to remove all detritus from a substrate in a timely manner, than there will not be an increase in P on the calcium carbonate in the substrate in contact with the detritus. there is a constant give and take between bacteria and the calcium carbonate for available inorganic P.

Phosphorous accumulation in marine sediments and the oceanic phosphorous cycle.

If this were not true, then the sand, live rock, and any other solid calcium carbonate in the ocean would be completely and irrevocably saturated with calcium phosphate. And it would be utterly impossible to leach this phosphate back out of the sand or rock as is commonly and repeatably done by hobbyists.

luckily for us bacteria like the P more than the calcium carbonate. they use the P for their own biological functions. all organisms need P for an energy source. only bacteria are able to access P directly from a solid media. even true plants have to wait until P is in an aqueous solution before they can utilize inorganic P.

Phosphate solubilizing bacteria

Phosphorus Uptake by Plants: From Soil to Cell

all of the examples of the phosphate cycle on Earth show that substrates are a P sink, and that erosion is main supplier of P back into the ecosystem.

G~

 

[dkeller_nc]

understood, but it seems like there is still a good amount of discussion left.

OK - a few more posts, but this discussion is a bit off-topic for this thread, so if you would like a broader discussion, I'd suggest posting a thread under the "Reef Chemistry" section with this subject in the thread title.

wouldn't the existence of an anoxic condition indicate that there is not an extremely quick diffusion between all of the layers? if the anoxic layer is just a few cm below the surface, than why wouldn't a solid like P also be increasing if a gas such as O2 could not diffuse quick enough between the water surface interface to maintain constant levels within seconds? something is not making sense? either there can be adequate diffusion to maintain equilibrium, or there can not be. wouldn't a gas have a higher affinity to maintain equilibrium, than a solid?

Not exactly. There are two things at work - one is distribution of a chemical species in a liquid (in this case, the liquid around the substrate in the sand bed) by diffusion and/or convective flow. The other aspect that determines what the concentration of a particular species is at any particular depth is rate of consumption and the concentration of the species in the bulk liquid. Diffusion is still remarkably quick between the substrate particles and the bulk liquid in the sandbed in this sort of system, but a gradient still exists between the top surface and the interior of the sandbed because the oxygen is being consumed by microorganisms.

The diffusion rate of chemical species in a liquid varies, but not appreciably for the purposes of this discussion. You are correct that diffusion in a gas phase is much faster than in a liquid phase, but once the gas dissolves into the liquid phase, its rate of diffusion is similar to other dissolved species.

you are correct if there is sufficient movement of media to allow for the equalization of P between the solid calcium carbonate and the liquid media. the problem is that we are not only dealing with P in the water, we are dealing with the P from detritus. it is this P that is causing the increase in P of the calcium carbonate media that is around the detritus. if detritus did not accumulate in our systems, than we would not have to worry about our systems increasing in P over time. if one were to remove all detritus from a substrate in a timely manner, than there will not be an increase in P on the calcium carbonate in the substrate in contact with the detritus. there is a constant give and take between bacteria and the calcium carbonate for available inorganic P.

I'm not saying that phosphate cannot precipitate or bind to aragonite or calcite in our systems - it clearly can. But it's not irreversible binding, and re-dissolution of the bound phosphate will occur quite quickly if the water's concentration of phosphate is dropped to low values. This will occur regardless of the source of phosphate - be it detritus, abiotically precipitated calcium phosphate, or the surface of dolomitic limestone. [/quote]



luckily for us bacteria like the P more than the calcium carbonate. they use the P for their own biological functions. all organisms need P for an energy source. only bacteria are able to access P directly from a solid media. even true plants have to wait until P is in an aqueous solution before they can utilize inorganic P.

There is no question that there are some soil bacteria that are capable of re-dissolution of solid phosphate, but I'd be cautious about extrapolating that to conclude that these kinds of bacteria are active in the ocean environment and in our tanks. Perhaps this will turn out to be the case, but perhaps not. You will notice, for example, that the phosphorus cycle diagrams that you posted don't include a large recycle component from ocean sediment back into the water column by bacteria.