Can anyone identify this mollusk?

Anihiel1 · Aug 10, 2021

I've searched google to no avail. Attaching pic of a shell from small one who was broken off by the clean up crew. There are larger ones all over my rocks. Couple of pics of larger ones but my camera is not the best. Had the rocks about 2 years now, suddenly these guys started popping up seemingly from nowhere. Also a pic of tiny clam of some sort? Several of those have appeared.
I'm assuming this is a good thing for the tank..? Or not...?
Pic 1 clam
Pics 2 & 3 larger mollusks in the tank
Pics 4 & 5 an empty shell

tjohnson3 · Aug 10, 2021

Look like stomatella snails to me… hard to tell from pic. Great clean up crew and super quick for a snail. Google image search stomatellas, and let us know if that’s what you’re seeing in your tank

Anihiel1 · Aug 10, 2021

tjohnson3 said:
Look like stomatella snails to me… hard to tell from pic. Great clean up crew and super quick for a snail. Google image search stomatellas, and let us know if that’s what you’re seeing in your tank

No definitely not stomatella snails, these are hard shelled mollusks attached to the rock. They snap shut if you shine a light on them, but typically you can see two openings (pic 3) like a bivalve.