Looks like a "decorator crab". Hardly classified as non-destructive to a reef tank. They like to attach pieces of coral etc to them as a defense mechanism (If I look like the reef, nobody wil eat me trick). Esp with what is riding on his back. Just keep an eye on him and your corals to make sure they aren't being damaged, esp when he decides to change his attire. From what I have read, they are not piscivere's, so fish SHOULD be safe. That's the first orange one I've seen, kinda cool.
