well if its cyano...i personally dont really see it as a bad thing, altho it can become bad if you just let it sit on the corals (it can cover them, they dont get light/food/whatever, and could possibly die...that being said, i've left corals covered in it for weeks and they showed no real problems).
But if its cyano, its more than likely just normal. All my tanks have gone through cyano phases in the beginning, and it always goes away as long as i keep the nitrates/phosphates out.
Anyways, its kinda hard to tell what it is just by looking at the pic (kinda too far away...). But is is slimey looking?
