Given a large tank, say a 180g for the moment, plus excellent filtration, addition of a heater, and fed twice a day on high protien pellets like sinking carnivore or dainichi and market shrimp, I'd say 1-2 years. For most people it takes a little longer. Heat will speed up its metabolism, so will powerheads. Your dat will need to feed more often and can stuff himself. Softer foods allow the stomach to be fully stuffed. Lots of different tricks to encourage growth. Good luck