"Shireen Gonzaga" wrote in message ...
I have a 20g microreef in the office. There's a black
algae coating the live rock that's difficult to remove.
It gets into the pores. It's a thin layer and does not
seem slimy. I try to brush it off but it always grows
back.

Are there snails or other critters that will eat stuff
like that? I'm also trying to grow coralline algae so
I've been avoiding algae grazers.

How sure are you this black stuff is algae
and not some sort of encrusting sea sponge?
Does it grow in the lighted parts of the rock
or rather on the shaded areas?

In my tank I have a large black sponge growing
shaded area of the rock in one cave...