Bear with me - Could be dead

Okay, so I'm just starting out my aquarium and I bought some live rock to put in.
One of the piece of live rock had a coral on it, and I thought, "what the hay, I really just want the rock so if it lives great. If not, too bad"

Well the store worker told me it was just a regular mushroom. However after four days now it has transformed into this transparent red-tinged bubble. It could very easily have died but it seems to move so darn much.

If this is a living thing, what is it? What do I do?

If not, like I said... bear with the beginner

(Pictures attached)

 

could we see pics in the white light? sorry! the actinics make it hard to determine!

 

Here's the white light. Thanks for taking a look...
I'm really quite a big researcher but have no idea what is going on

 

That is weird looking. I'm curious as to what it is as well.

Have you touched it to see what it felt like?

 

Have not touched it, however I do believe this thing is alive. Since turning on the white light I was able to see what I believe is a sweeper tentacle roaming around.

What fascinates me is this started as a very dense lump of a coral, which was I expecting to flatten out like a mushroom. And instead it is a bubbly little thing turned transparent tinged with red.

I'm grateful for any suggestions.

 

What I see looks like a bacterial bloom and should be removed. Run some quality carbon as well and do not add anything to the tank for a week or so.

 

+1

Possibly from dead tissue on the rock.

 

Yeah, I believe I will remove it. That seems to make sense, and I definitely had no plans to add anything soon.

Thanks for a taking a look, I just wanted to know what was going on with this thing.

Thanks again everyone for their replies.