New tank. Started running with water, sand, LR about a week ago. I am using the LR to cycle the tank; the LR was purchased the same day it was received at the LFS, and as of today, no known hitchhikers (minus a bunch of amphipods!). At about day 5 I started seeing diatoms on the substrate and the LR. By today, it's covering the uppermost parts of the rocks pretty well, and have nice brown polkadots in the sand. My question is this though: What is this white substance/fungus/slime/whatever that i see in the crevices of my LR?