Refugium hitchiker ID? (slug'ish)

[GoFish]

I found this little slug on the back wall of my refugium a couple hours ago, i didn't bother catching it as it looks a little small to do any harm. Its beside a snail in the picture which is about 3/16" around and the slug measures 3/16" wide X 1/4" long approx...
Thoughts, or suggestions?
Its the color of sand or coral