I'm trying to recall what it may be but I have what looks likes dark brown/black splotches on the live rock. It looks a little like pepper. I don't believe it comes off easily. Diatoms? Dinos? I've had snails dying off and thought perhaps dinos even though I probably had more than the tank could handle. My coralline growth is fairly sparse right now, but I've only had the tank running for several months.
RK
RK
