Commercial hatcheries feed train bass when they reach about 2 inches by concentrating them in tanks and warming the water to increase metabolism. It's imperative the tanks are kept clean and many add formalin or something similar to keep bacteria down in this crowded conditions.
The larger a bass is the more difficult feed training will be.
If it was me, this time of year I would bring them inside into an RAS or flow through with heated water and concentrate them dense enough to allow competitive feeding to take place. Start with natural feed and gradually phase into hydrated pellets and then hopefully dry pellets.
Buying feed trained bass would be much easier and cheaper!
