16-24" You will need a larger tank (180g minimum). But they usually grow extremely slowly and wwon't even pass the 12" mark until they are over 2 years old. I got mine in February at about 5-6" and they are both only about 2-3 inches larger now than when I got them.
But not for ever apparently...yeah not so much interested in getting one only to part with it one day. I'm not the guy that buys a fish with plans of upgrading the tank later. I get the fish thats suitable for the tank I have now. Thanks for the info everyone.