I feed them good food and keep them warm and the water clean. That is pretty much it. I use Ziegler's Finfish Silver 3 mm floating pellets. The males put on weight fast if they are not too crowded.

The Oxy tank is for shipping fish. I use pure O2 rather than air. The duct is from my furnace on the other side of the wall.

MY system is pretty simple. 100 gallon stock tank as a sump. 1/2 Hp pool pump taking suction on it, and discharging to a pool sand filter using plastic beads rather than sand. There is a distribution header that brings water to all the tanks. Overflow pipes take the water back to the sump. I also have an aquacube bio flter in the sump and 2KW of heaters.

You can see my setup here:
My 700 gallon basement system