A slightly more contextual quotation from the statement that I made.
Originally posted by barryhc
It is now below this "low oxygen" zone, that other processes are carried out by OBLIGATE Anaerobic bacteria, and it is here where Nitrates and other nutrients and compounds are processed into nitrogen gas supposedly, which is somewhat controversial for some reason, and hydrogen sulfide ( again contrversial ), Phosphates "bind and leach", heavy metals "sink", and again, guess what, all controversial.
I believe that all these processes occur in a deep sand bed, to one degree or another, and likely, different in every tank. It is the DIFFERENT in every tank part that has gotten us into this discussion, I'm sure, along with many other things.
<a href=showthread.php?s=&postid=6479600#post6479600 target=_blank>Originally posted</a> by Sindjin
I disagree. PO4 will "bond" to Calcium Carbonates such as Aragonite. There have been many studies on this.
What do you disagree with?
The "controversy" is that you must understand that this "bonding" is pH dependant.
Among other things. I agree whole heartedly!!!
Most of the bonding takes place at a pH of 8.4. If the pH is significantly lower, it would reverse this bond, leaching the PO4 back into the water.
Well, kinda-sorta. Actually Phosphate becomes less able to precipitate with calcium at levels both above AND below the 8.3 to 8.4 range of pH. And you are right that it is the lower pH values that occur at some depth in a sand bed, and inside of live rock to some degree, that causes Calcium, Carbonate, and phosphate, along with some heavy metals, to be released from the substrate.
Now consider this, how did this Phosphate get there in the first place? Well some of it is in the Araganite to begin with, and this is why I'm not quite so keen on it for a substrate choice, especialy in "fine mud" grain sizes, but I digress.
And of course we are going to keep the poop out of the bed with high flow, good grain size, and skimming, and critters, but phosphate can still get into the bed the same way ammonia does.
If Phosphate is released from the mineral state with Calcium, then it is now in the pore water. It does not spew out of the surface of the bed like a fire hose. The release of various compounds including Phosphate certainly does occur, at least while "buffering" is occuring, and quite possibly while stirring or other maintanence is going on.
pH levels of ~ 6.5 to 7.5 have been identified as particularly "good" levels for "buffering" to occur, and the phosphate is likely to "release" here just as well. And the finer the particle size, the faster the releasing, as well as clumping or crystilization if the pH changes substantially, quickly, and remains so for an extended length of time.
Again, I wonder about Araganite as the best choice for substrate based on this. Ditto for the "mud" grade particles.
Now the Calcium and the Carbonate are going to get back into the water column by some process, and phosphate might do this as well, BUT there aren't any animals in the substrate to eat the Calcium and Carbonate, whereas it is a different case for the phosphate now isn't it?
The phosphate will run into all this biological activity that loves to use it as a food source, and it doesn't only go up either, now does it?
Well, is that enough for now? Maybe some one would like to chime in, and finish the story!!!
Thanks all !! > barryhc
