Oct 17, 2006 #1 R rocky79 Aquarium Advice Newbie Joined Oct 13, 2006 Messages 6 Looks like white cotton, but ony on one of my rocks (inside the thin red circle).
Oct 17, 2006 #2 Fluff Aquarium Advice Addict Joined Apr 30, 2004 Messages 11,423 Location West Virginia They look like harmless sponges.
Oct 17, 2006 #3 melosu58 SW REEF 20+ YEARS Joined Oct 21, 2004 Messages 39,152 Location Virginia Look like sponges to me also.