What is this bivalve thing?

[GHsaltie]

I was gifted a very large toadstool a couple days ago and before dipping it I noticed this little shell thing on the rock.

I snipped it off and put it in my tank. I did notice a reaction from it this morning while I was feeding so it's definitely still alive. What do you guys think? Is it just one of those no-name bivalves that pop up randomly? Is there anyway I can try to keep it alive?

 

[Lionfish Lair]

Yup, it's a little bivalve. It may live it your tank without any intervention from you. I wouldn't do anything, in particular, to try to get it to live.