need hitch hiker shed id

[JenniferL]

This guy came as a hitch hiker on my LR. I have only seem a few quick glimpses of him through holes in the rock. I found his shed a couple days ago and wondering from this if anyone can tell me if he is bad. I do have some corals in my tank now, but I'm thinking he doesn't look very reef safe. The shed is next to a teaspoon so you can get an idea of how big he is right now.
thanks