My future mantis tank (cycling right now) is a pretty bare bones system for a small P. ciliata. It depends on what type of mantis you are getting. Do you have anything in mind? If you tell us what you are thinking about, we can give you an idea of the mantis' requirements. If you are thinking about a peacock you need a 30 gallon pref. with live rock, good flow, a protien skimmer and U.V. sterilizer. The good flow and U.V. sterilizer are to ward off shell disease, and a protien skimmer to help keep waste down because they are messy. None of the above is absolutely *necessary* however (except the tank, of course) but can help improve the animals health alot. All a mantis really needs is good water, good food, exercise, some room and a burrow.