What Are These?

[Demm]

i've never noticed these before, and now out of no where i have about 5 or 6 of them, probably more that i'm missing. i'm guessing it's some type of filter feeder. i dont think they really move. are they ok to have? are they dangerous at all or anything? they look like sponges mixed with a featherduster?

thanks for the help!

 

[Donya]

Some sort of calcareous sponge maybe? I have some that look like that (sort of along these lines: http/www.cartage.org.lb/en/themes/Scienc...calcisponge.jpg )

 

[SkiFletch]

I'm not entirely sure what they are, but they're definitely filter feeders and my reef is loaded with them. They usually migrate/grow underneath rocks or in dark areas of the tank and avoid the light