Its not a crab i am familiar with but at a guess i would say its not safe for your tank. The reason i say this is becaus eof its claws. Id the tips of the claws end in a spoon shape then its predominantly an algae eater and poses no threat to healthy fish, (all crabs are opportunistic and will take sick or dying creatures). If the claws end in points then its a huntr and may well prey upon your tanks residents.