Algea??

[Alf]

New one for me if it is. Kind of leathery, and encrusting. If it is? any known predators?
Thanks to all.

 

[IowaKGB]

Looks like sponge to me. Not sure what eats it. Maybe certain types of angel fish?

 

[hnurge]

I 2nd that - yellow sponge (not photosynthetic). i think hermit crabs may eat it - not that i have seen that happen, but something must, because it stays in hard to access undersides and crevices in my tank. I never considered it a pest - just part of the healthy reef fauna.
however - from cleaning algae\dipping new corals I have found that a squirt of peroxide (3% H2O2) will kill it quick.

 

[Fish Think Pink]

+1 yellow sponge - my flame angel loves mine - I only have it where my flame angle can not reach sponge (deep crevices, etc). Agree not photosynthetic.

 

[Alf]

Thank you for the responses. I was hopping as much. But didn't want it to get out of hand if it was Bad. This is a reset to a new location in the house and new sand bed, tank was set up in 2000.