What is this stuff on LR


Reef enthusiast
I just noticed this grey stuff on this piece of LR. What is it? Do I need to scrub it off or leave it? I wouldn't of worried about it but it's where Tony hangs out.

Piggy did you once have cyano?
Honestly I'm not sure what it is.
If its not dead/dieing cyano then maybe dinoflagellate?I would definitely siphon it out if possible.
I did have cyano in my tank but not on my LR. It was on my substrate. It won't suction off so should I take it out and scrub it off?
get yourself a good firm-bristled toothbrush for cleaning rocks, they work great to get into the knooks and crannies. I agree with reef about cleaning it off.

-Dr Marco :sfish:
It almost looks like pink sponge to me... If it's just pink sponge, that's perfectly reef safe, and prefers to grow in darker areas of the tank.
Looks more like dead cyano to me.But if that was the case it would siphon out.
So I'm thinking like Reef.Take the rock and srcub it with a tooth brush.