Good luck dude they grow pretty quick in aquariums, and as far as pellet training it can be done but if yours is WC it's gonna take a while(went to a hatchery where there were isles of vats with LMB devouring pellets). As far as outgrowing that tank I'd say a year or so if you power feed him. Also your going to want to keep the water at like 70ish for best growth conditions.