Enjoy it in the bag because once you put it in you will never see it again. Seriously though they are aggressive towards other inverts and if you have live rock that isn't secure they will burrow under and topple everything. That being said I like them but you really have to consider what inhabitants will be in there and treat it similar to a mantis shrimp and their requirements.
Ooooo.... I'm not going play that game. When you read information on them in the online fish stores they don't sound too bad. I'm glad I asked on here. I don't mind him hiding but I don't want to lose any other inhabitants. Thank for the insight!
I got rid of mine. I saw him get a yellow neon goby in its pincers. I was able to scare it and saved the fish. It got a hold of one of my mandarins, munched its tail and had symmetrical scars on its torso from the pincers. I would be cautious, you probably will never see it except maybe at feedings.
I have one in my 110. I am never sure he is still alive until he molts and pieces start floating around the tank.
Every once in a while I see him if I look quickly when I get up early.
He was in my 12g nano for awhile and never bothered anything or anyone.