I would agree. These big cats need high protein low fat diets. Thats why we aren't feeding these guys hamburger and things like that. You can feed liver and fish fillets though. for the big guys you could even feed whole frozen fish. (make sure they aren't really oily fish like anchovies though) I've heard of some guys feeding their big cats hotdogs, but not as their main diet...
Jumbo Prawns make great food for TSNs this size too. I just lost mine, but loved it. They are awesome fish.
And I don't know how much your dad pays you... but your going to have to work more than every couple of weeks... When they get big and can scarf down 10 jumbo prawns in one sitting easy, prices are gunna start stacking up.
I know every ones tellin ya the same stuff, but we just wanna make sure you know what your getting into, and watching out for the fishes sake. It all looks really good on paper or in your head, but when it actually comes down to making it happen, its a completely different ball game.