a mantis shrimp has two club like claws that they use to stun their prey with. It has been mentioned that the club has the same force as a .22 caliber bullet. I was unforunate enought to have to in my 65. The first one I caught after killing over $200 in fish. The second one I caught after that little F@^$@er cracker my All-Glass tank. I think they are cool looking shrimp, but if you want to keep them, put them in their own tank. I do not consider them reef friendly or fish friendly. One other note, the last mantis in my tank whacked me on my fingers as I tried to net him. It pretty much feels like someone hitting you as hard as they can with a metal rod.