well many amimals will grow to the the limits of their enviroment (food availability, size), if they are in a small tank, they will not out grow it, at least quickly . if you put that same one in a larger tank he will grow bigger. I guess the key is if you are moving him from a smaller tank to a larger one and he showed no stress in the smaller one, my guess is moving him to a larger one should be no problem and he will just get bigger. mine in the 75 gal has stabilized in size, he looks happy and still eats well. I would like to get him into a bigger home but I am not too worried about it based on his current behaviour.