ID Please - Mystery Clam-esque Creature on Live Rock


New member
Hey guys, I just noticed this mysterious creature today on my live rock. It's about the size of a dime, maybe a little smaller. It opens and closes periodically, when closed it looks like a tiny flat clam, when open there is webbing between the top and bottom.


Anyone know what it is?

Thanks in advance

Just bumping you up. I don't know what that is, but I've got something that looks similar at the base of a Pagoda coral. I've been watching it for a few months now. No change and no apparent harm. It is mostly hidden from view but it doesn't appear to be harming anything. The Pagoda looks happy.
It's a clam. They come in on LR as hitchhikers all the time. What species of clam I don't know, but they are just harmless filter feeders.
Looks really thin when it's closed, I'm pretty sure it's a Pearl Oyster (Pinctada species) rather than a clam. There are several that look similar to yours. Again, it should be harmless in your tank.