[Zoaelite]

I think this is the rare fuzziephoto limpitis. I have tones of these guys in my fuge (atleast I think :S) They remind me of slugs but there very good for cleaning algea of the glass I think there called Stomatella Snails, then again it could just be a Chiton or a Limpet.
Info on Stomatella Snails:
From Melves:
Many people ask about a snail or slug with a half-shell on its back. They are called Stomatella, and are fast moving slugs. Their shell is similar to a fingernail in shape, which covers the head and torso of the creature. They are found moving about the rockwork especially at night, and are an excellent part of the clean-up crew. They do breed and you may see smaller ones, but I've never seen them reach plague proportions. Reef-safe. Another image by Gregory - 202k

Levi