+1. pick a species first then ask again
. O. scyllarus (the true peacock mantis) for example needs a 30g tank and is capable of breaking thin glass. N. wennerae and G. smithii on the other hand will be plenty happy in a 5g and aren't capable of even chipping glass.
here's a good site to help you choose.
http://www.ucmp.berkeley.edu/arthrop...ist/index.html
you should also be aware that lfs and online vendors virtually never ID properly. I can think of three suppliers that id reliably but they're all american.