Mantis shrimp make great pets. They are incredibly beautiful and intelligent. An acrylic tank is probably best, if they get too big they can crack the glass. My girlfriend had a couple of Odontodactylus, (not at the same time) and they were just about the coolest pets we have ever had. I think you can get them from special order from just about any store. We get them from time to time at my work ( I work for a wholesaler) so they are out there.