Mine are in a 50 gallon. I know they'd be happier in a larger tank, but they seem to be doing fine in it so far. I wouldn't recommend putting more than one in that size of tank, though, unless they'll get let out for exercise often.
i have both of mine in 40 gal tanks. . . i think im going to upgrade to a crossfire one when i figure out where i want to put them. my older one 18in's has a hard time turning around.
Right now mine is in a 33 gallon breeder, but it is way too small. We are building a much bigger viv, so Roxy is just outside of her tank a lot for these next few weeks.