Any idea what this is?

[falesdk]

I bought a half lb. piece of rock to shield my alveopora, and two weeks later it has this brown stuff growing on it (the rock, not the coral). Is it a sponge, or something that needs removal?

Thanks!

http://i60.photobucket.com/albums/h37/falesdk/100_1769-1.jpg

[acrodave]

looks like sponge to me . the stuff on the sand looks like cyano or diatoms

[sassafrass]

looks like a sponge to me , it is good because it performs filtration , looks like a little cyano bacteria on your sand {usually caused by phosphate } And a low flow area
Regards , Lee

[falesdk]

yeah I have an ongoing battle with cyano on my sand. it has receded to this small corner of the tank though so I do feel as though I'm winning :) Oddly hermits and snails just cant seem to live in my tank, even though I have no trouble keeping other inverts. Oh well though, I'm still winning.