That Mantis Shrimp thing isn't quite true, there are tons of aquariums with Mantis Shrimp in them, you just better not put anything else in there also most people use acrylic aquariums instead of glass(even though really only the largest species would be of glass breaking concern). Lots of people keep them as pets. The biggest Salt Water aquraium message board on the net has an entire section devoted to just mantis shrimp. I love going in and reading about them.