What is this thing?

[Goatonfly]

This thing was on the bottom of my live rock yesterday, now it's on the back. I was hoping someone could tell me what it is so I know to remove it or not.

I'm not sure what the black stuff is either.

 

[billdogg]

The black "stuff" is a type of encrusting sponge - filter feeder, good.

I can't really tell what the other thing is, but if it's moving, I'm leaning towards some sort of nudibranch, very possibly bad

 

[SNAKEMANVET]

It appears to be a mollusk of some sort.

 

[Goatonfly]

I tried suctioning it out and I moved it. I got a better picture. But then it fell in between the rocks and I can't see it anymore.

 

[Goatonfly]

What about this little guy? It's kind of cool checking out this live rock piece and finding new things on it.

 

[SNAKEMANVET]

Hard to tell from that pic,kinda blurry.

 

[billdogg]

The first thing in question, upon looking at a better picture, is a bivalve of some sort