Feb 1, 2011 #1 the_fish_man Aquarium Advice FINatic Joined Jun 8, 2010 Messages 988 Location Colorado Wondering what this is
Feb 1, 2011 #2 I Innovator Aquarium Advice Addict Joined Nov 18, 2006 Messages 3,462 Hard to tell without a clear shot, but I'll guess a hydroid colony on a rock.