It's a dark brown body whit white tips at the end of its claws, it's legs are hairy with white and gold stripes and godt tips. It's about the size of a quarter. I need a better pic.
Yep, get a better pic and maybe someone can tell you.
I don't know my crabs very well but I think I can safely say it's not an emerald, sally lightfoot, or arrow. I tend to agree with Dogstar though. Those claws look like fish grabbers to me!
I don't think they would do any harm to anything in your tank. Here is what SWF.com says about them :
"These crabs feed by extending their maxillipeds, which are designed to catch plankton which they then transfer to their mouths. These are great little crabs for any reef aquarium. They will spend most of their time in the comfort of rock crevices. Porcelain Crabs can be kept in large groups if enough rockwork is present. They should be provided an aquarium with a good water flow."