Nudibranch?

[Rutrag]

I wasn't able to grab a camera fast enough to snap a picture when I saw him, but I saw a critter in my tank this morning which I think is some sort of nudibranch that came in with a coral. I had actually seen it the night before, but it was still, I guess in some sort of dormant state sleeping on the glass. In that state, he was basically oval and the size of the limpets I had seen before on my rock, and I thought that was what it was.

Today, I saw him moving about in a somewhat elongated oval/ teardrop shape and he had antennae (which he had to have pulled in the night before) and was moving FAST (at least for a snail-like critter) over the live rock until he ducked down between a couple pieces. He's kind of a tan color (about the color of a sea hare, but not mottled) and is a little more grayish at the center of his bodyand pretty flat. Any ideas?

If I can snap a photo of him or make a video, I'll post.

 

[Rutrag]

I think it might be one of these:

Stomatella Varia - A very commonly found hitch hiker. Harmless herbivore which has a unique way of fooling predators. When attacked or pulled off the glass by us, it will drop a large portion of its foot, much like some lizards that break off their tails in an attempt to keep a predator busy while it makes its escape. Keeping to their descriptive species name, they are highly variable in colorations.