Can anyone ID this hitch hiker nudibranch? Coral eater?

Several weeks ago I added a new coral to my tank, a gregorian coral, and it came with a cute little white sea slug of some sort. I had pulled the slug off the coral and moved it to the other side of the tank. The tank is only 29 gallons, so that is not far, but it only took about a day for this little guy to find the coral again. He has never left it. He moves all around the coral everyday and stays on it. I cannot see that he's doing any damage to it. The polyps pull in where he's at, but those same polyps extend later when he moves. I had been watching for signs of damage. I am curious though.... what is this nudibranch and is he doing any harm to the coral? I've kind of taking a liking to him, so it's not likely I'm going to remove him.

Oh no! That isn't the response I wanted! Ok well I wanted to know what it's really doing, so thank you for giving me the answer, but what damage can it cause? I was hoping it was maybe cleaning the coral. You can see where the polyps are pulled in during this picture, however they fully extended later, leading me to believe the nudibranch isn't actually eating the polyps or anything. It's such a cute little parasite too! Did I really just say that? :screwy: I will continue to watch it closely.

I am also adding a full tank shot below so you can see the actual size of this, just to put in perspective how small it is. This is a 29 gallon biocube and the gregorian coral is on the right hand side behind the larger onyx clown. The nudibranch is just a little thing on that coral. Due to it's size, it seems pretty harmless. Is it possible for it to reproduce rapidly and take over my tank? I'm pretty certain it is the only one in the tank.

SubRosa said:

Good luck. There's quite possibly more than one.

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Yeah that's what I'm wondering. I was just adding to my post wondering if there could be more than one and if they can multiply quickly. I am one of those people who can't squish a spider. I really hope this little guy doesn't cause any damage. I've seen some places sell nudibranches... I assume those are a different non-coral eating variety?