I have a black sand. It may be dirtier than what I see, but it is not clumpy. It is not super fine grained. The flow of the tank moves across it rather quickly.

I have lots of nassarius snails and I have some hermit crabs, but not many, probably 5 or so.

I move the sand around occasionally, but the nassarius snails do a lot of that during feeding time. It is very plague like.

Silica, I haven't that of that. I will have to ask them about that.