Clam in my new Zoas?

Got this guy yesterday. He was "crackless" for awhile then started opening up then closed again when the lights were off.

The pics aren't great, my camera wanted to focus on the other corals in the front. It's opened up even a bit more since I took these pictures a couple of hours ago.

 

Here it is opened up a little more. I can see something inside but I have no idea what it is

 

thats wierd

 

i have one of those in my zoas also, i assume they just filter feed

 

That's weird & scary. Are Both this mysterious clam and zoa attached to a rock rubble or zoa is attached to the clam?

 

your right they do, great for helping filter their little part of the reef

I have a piece of base rock from a long ago attemp at saltwater that turned out to have 3 or 4 of them embedded in it.

 

Do clams hop? I saw it jump!

 

Yes, they use their foot to move around.

 

in a way they can. if they expel enough water through them quickly , they can kinda move. that could be some type of mussel or other bivalve, not sure its a clam. very cool tho