Little clams or something?

[kammycat2002]

I found these little clam lookin things in my tank that I don’t think were there before. I’m pretty sure they’re alive too cause I picked one off the rock and it was holding on pretty good. The one on the rock also had its mouth open and then closed when I poked it. Does anyone know what these are? Are they pests or can I keep them in the tank? The one in the rock may be hard to see because of the algae so sorry about that.

 

[ISpeakForTheSeas]

Looks like a mussel of some kind to - they (and most other bivalves) are harmless filter feeders and should be fine to keep.

They’d likely benefit from some phytoplankton.