Apr 7, 2013 #1 george9617 Aquarium Advice Regular Joined Nov 9, 2012 Messages 95 This stuff is strange I have no nuisance algae and this stuff is spreading on one rock. Any ideas
Apr 7, 2013 #2 Massimo Aquarium Advice FINatic Joined Nov 5, 2012 Messages 534 Possibly a sponge, I have one in my tank, it's harmless unless you don't like it