While adding lr to my new tank, I was given a piece covered with star polyps. While looking at the piece (which is open and doing well), I noticed what I thought was a worm in a crack. Went to pick up my magnifying glass, and it closed shut. Apparently I have some kind of clam, and wanted to see if anyone could identify it?

This is as open as it gets.

The featherduster?

No not the featherduster. The thing that the featherduster is attached to. It opens and closes, so it is alive? I thought it was just a round part of the piece the polyps are on.

Any way you can get a better pic?

It opens and closes long-ways like a mollusk or it has two circular openings?

long ways. It is actually open in the above picture, just above the featherduster is where the mouth/opening starts.

Photobucket is being evil, and it is closed right now anyway, so I will try for better pictures tomorrow. I tried seaching for something similar but came up empty.

Could be some kind of mussel. I had one ride in on my rock years ago and have seen other 'round here who've had them. They generally don't live long... Probably starve.

I take it that this is the mollusk in question? Hmm, I've had similar ones hitchhike on some rock before, and they're still alive. They're in my chaetomorpha tank though; I add some invert food occasionally to keep the amphipod population up, so that may factor in.

How long have you had yours, carbon?

I've had the larger (maybe 2-3" across) ones for about five months now, and some small cm. sized ones for about a year. I don't think I can say much on the larger one's health, other than that they're still alive. I'll see in a few months or so, I guess. As well, I'm not sure if the larger ones are the same species as the smaller ones. About the only similar traits they share is that they're very difficult to distinguish from the rock.