I have a juvenile Red Eyed Tree Frog and he's currently in a 12"x12"x12" Exo Terra Terrarium (I know that Tree Frogs are supposed to be in vertically oriented cages but I couldn't afford one at the time). So money is tight and I want to get a cage that he'll be able to live in for the rest of his life (We're just assuming that it's a boy). Should I go with the 12"x12"x18" or the 18"x18"x24"?