<a href=showthread.php?s=&postid=11212505#post11212505 target=_blank>Originally posted</a> by Frick-n-Frags
I wouldn't even know where to start, except to say that you are really missing the big picture here.
whatever you are talking about isn't the realities of the reeftank substrate, more like a chemlab experiment.......
No chem lab... I'm just going with occam's razor using basic well established facts...
The simplest explanation for sand clumping is overdosing ca. Agaronite, is a calcium carbonate crystal, similar to calcite (limestone). If you have a clean crystal surface, calcium will, as Rosseau put it, flocculate and the agaronite crystal will grow. I believe this happened here because instead of monitoring both ca and alk, and trying to add them both in balanced moderation, ca was added and combined with the carbonate forming CaCO3 and crystallized into more agaronite. Additionally, jefferzbooboo said only ca was dosed, so there was not enough mg to disrupt the agaronite surface allowing rapid crystallization. The ca levels dropped and more was added and the clumps grew...
(So in other words, there was sufficient ca to force both ca and CO3-- out of solution - this is enhanced due to a clean crystaline surface).
The worm cast idea is reasonable, but it seems somewhat unlikely that you would get “cigarette pack†sized clumps from this.
The problem with the bacterial induced sedimentation is that it occurs because organic molecules such as proteins and glycoproteins (and others) bind to the agaronite surface and prevent phosphates and magnesium from binding. Because, phosphates and magnesium inhibit the growth of the agaronite crystal, there is now no inhibition of crystallization.
However, the theory is not very well established, but there is evidence that inhibiting protein synthesis does decrease calcification considerably. Regardless, there still needs to be sufficient ca,so overdosing ca, and under-dosing mg, is still the real issue. In this case, mg isn't being dosed, so it's effect will not be inhibited much anyway â€"œ because there isn't much of it anyway!
Frick-n-Frags, you seem to understand a lot of important concepts, but I think you maybe dont't quite get the concept of crystallization...
