I also agree that it is a stomatopod (= mantis shrimp). You may want to move it to a Q-tank or a bucket with aquairum water, provide lots of rubble or other hiding places, and then remove the coral after the mantis has moved out. Beware that one pair of appendages are (usually) modified to be raptorial - essentially they have switchblades for arms and can inflict a serious injury on one's hands. Even if it is small it could be dangerous. There is an entire forum on this website for people interested in mantis shrimp. They are a pretty ancient crustacean taxon and have very complex behavior, thus they make interesting pets. Someone would probably gladly pay your shipping expenses if you were to send it to them. Otherwise if you are going to destory it, I would take it and pickle it for my department's invertebrate zoology specimen collection.
Kevin
