depends on the dimension of the tank.i would say 6x2.5x2.5 is the bare minimum. the bigger the better. you could house it for 2 years atleast and then look to upgrade.
There are many that have kept a silver aro in a 180g 6x2x2' for many years. IMO once the aro reaches 26-27" it needs a bigger tank. Starting with a 6" aro, you would be looking a 3 years at the most.