barnacle with my live rock?
 

I just found this weirdo clam hiding in one of the caves of my lr. It's not a flat clam shell... more like an oval, like a barnacle. Its about an inch long and half an inch wide, and i would like to keep it. I dont have anything else in the tank except for live rock currently, do i need to do anything for it? It hasnt really opened up yet.

thx

a chiton?

not really, really looks like a clam shell, but it opens up a little bit, and some kind of snailly kind of stuff comes out a bit.

a scallop?

picture's worth 1000 words, as far as keeping it, supplement it with some phytoplankton or another filter-feeding suspension 2-3 times a week and maintain good calcium and water quality : )

i think DJ guessed it.a scallop.its probly opening and feeding at night.

I want to say Brachiopod. I have two, and it resembles what you are talking about. But, these are usually stuck to the outside of the rock, and not in a cave (but I'm sure it can be in a cave).