The most common are the silver aro(South America) and the jardini(Australia). The adult silver will get well over 30" and would need at least a 96x30x24" but would to better in a 96x36x24" tank as a minimum. A jardini will get upto 24" and a 6x2x2' tank would probably work, a 6'x30"x24" would work for sure.