Use massivore and Talipia or shrimp. If you use masivore get it wet and squish it into a ball just big enough for him to eat. Talipia is the best IMO sense its cheap, and healthy. Also give him random things like I do. I feed mine every night with tilipia fillets until hes full (when he no longer comes to up for food) but he gets random treats like banana, worms, massivore, tadpoles, octopus today, shrimp, scallops and other crap at random times during the day or night. I would say the number 1 thing in growth is water. I do a 50% wc every 2 weeks in the pond but when he was in the grow out I had the drip setup to change 40% a day. My ID sharks have doubled in size because of the frequent change over in water. Water is on top with food quality in growth factor IMO