Any ideas what this is?
 

I thought these where new anenomes starting but then I remembered they looked the same a month ago when I bought the rock. Sorry for using video, but my camera and camera on the camcorder just couldn't get as close up and clear.

YouTube - MOV007 <- 6 Megs

Thanks

looks like a sponge.

Ken

+1 on a sponge, I have a few of them in my overflow's and sump.

Give em enough time and your overflow will be filled with them.

Mine is, but I do try to scrape them out of the sump if I ever see any. And also pick them out of the DT if they start growing.

Thank you
 

Thanks everyone. I should remove them then? I have 4, and they are the same size as they were when I go them a month ago.

If they are not in plague proportions I wouldn't bother removing them as they don't do anything harmful to the tank and might even benefit it.