Mystery Live Rock Hitchhiker Clam/Oyster?

[jshaw1980]

Hi everyone,
This is my 1st R2R post, I hope somebody can help me identify what this thing is attached to the live rock in the photo that I attached. I originally thought it was some kind of egg as I have barnacles that appeared in this tank out of nowhere. Today I noticed that is egg looking thing was open and I shined a light on it to inspect it. As soon as the light hit this creature the shell shut very quickly. Any ideas what this could be? Thanks!

 

[Reefhabit]

Its a bivalve...lol. Neither....looks like a muscle to me. Leave it be. They are good filter feeders.

 

[Reefhabit]

Oh and welcome to R2R.

 

[jshaw1980]

Awesome! Thanks Reefhabit!!