This guy is slightly bigger than a dime... no threat to anything else in the tank but cyano. Yes, cyano. Couldn't believe he was actually eating some from a small patch in the tank.
I'm sure there's a wide variety of subspecies within the spider crab group, but these are the small ones that can be found in the shallow reefs in the Keys. I've pretty much nailed down how to get them to use zoas, so if you're interested in one, shoot me a PM. They are unique!