I would not put that one in my reef. Keep it in the sump for a while and feed it there if you like. Small hairy crabs are often acro destructive and with claws shaped like that are often killers of things many times their size such as snails and clams. If you can find an exact species id later and it comes out ok, then you can change your mind and put it into the main tank but it does look like one of the ones not to have in there from the pics. Many of these start out peaceful scavengers and then turn into ugly gang members and wreck things later on.