I thought I read something that aragonite we'll just find together on its own for some reason but I just can't remember what exactly.
Randy you made a good point, when I broke my Fluval system down that's when I noticed all of my sand bed in the one rear corner was basically like a brick. I always struggled maintaining higher phosphates but I did for a while at that Marine buffer but I didn't notice the sand bed binding whatsoever.
We only had one case of severe precipitation that coded the heater housing and sections of the glass. We corrected that issue with a water change to bring things down. So my question is if you wouldn't mind explaining is what does phosphate and nutrients at a higher level have to do with sand bed calcification?
See when I commented about flow when it happened to me it's because I had a whole bunch of rocks in the back corner and chalked it up to really low flow. All that other stuff the Fluval went through was before I changed the rockscape. I just need an understanding of how the nutrients and the phosphate work when it comes to the sand bed locking up.
I am not aware of any studies that show exactly how sand grains adhere to one another in a reef aquarium, but there are a few facts that give strong evidence that it is precipitation of calcium carbonate cementing the grains together.
1. The effect is much more likely on new sand. New sand does not have its surfaces protected by phosphate/organics/bacteria/magnesium and hence it acts as seed crystals for precipitation much better than old sand.
2. High pH and high alk often leads to hardening sand. Those two factors are the main driver of precipitation in a typical reef tank.
Thus, IMO, it is clear that sand hardening is abiotic precipitation of calcium carbonate.
Sand grains do not just attach to one another without some new chemical getting between them and adhering them together.
Heat reduces the solubility of calcium carbonate. Thus, any warm object such as a heater or pump impeller will tend to collect some precipitation.
Phosphate would, IMO, tend to reduce the chance for calcium carbonate precipitation by "poisoning" (that's the term chemists use) the crystal surface for more calcium carbonate precipitation. If phosphate is high enough, one may have the whole binding effect with calcium phosphate, although I do not know at what level that would kick in, and whehter it is attained in reef tanks.
I don't think nitrate has much effect, except if it encourages organisms such as algae or bacteria to grow on and block the precipitation of calcium carbonate on sand grains.
I'm not expecting flow to play much role.
