Sparky477
Aquarium Advice Apprentice
I found this critter on a rock and then roaming around on one of my button polyp corals. I took him out for this photo and dumped him back since he looked harmless. I figure he's some sort of Gastropod like a limpet, but his shell is a little small. He's more like a slug with a hat.
I have more photos at www.weirdthingsinmytank.blogspot.com which has a larger version of the above photo.