We got this coral a few months back and to be honest I thought this dude was glue or something (I know dumb, I'm still new to salt water tanks) but today I noticed thr zig zags and had been watching closely when I saw it open and close. Scared the crap out of me. All I know is that's not glue. It looks like a clam but I've never seem a clam attached to a coral before. My question is is this a clam and is it OK for my coral