:36 by 18 gives aboyt 4 and a half square feet of space so when its more than 5 inches long its really too big for the tank. I'd say you'd get away with six months to a year at most.
:They grow medium fast and yes they are sedentary but they do get huge. You will eventually need like 20 square feet for an adult. A stock tank is a more realistic long range plan.
Ahh thanks for your help again ;) I had one for a short time a long time ago and it never got over 5" so I wasnt sure on how big they got and how fast they got there. I had saw a real nice one in the clasifieds so I figured I would ask.