These are a slower growing species. You are going to want to do a large water change at least once a week, and feed a variety of high quality foods. Pick a nice, high quality pellet like omega one, NLS, tetra cichlid sticks, or hikari, and mix that with some frozen and freeze dried foods.
I understand that a male should hit about 6" in the first year, and it takes at least another or two to reach a large size.