I've got a few but they're bigger and black. It does appear to be alive. As soon as they die, their shell usually opens up. I've never known a hitchhiker clam to be a problem. If it were in my tank, I'd place it in a divot on a rock and see what happens. I have one that I've never seen open but after a few weeks in one spot I tried to move it and it had attached itself to the rock.