I used to keep largemouths in a tank for years but have moved over to the legal way to do it with a Peacock Bass I got at a local Aquarium shop.

The only way I ever got my bass to eat something that was not alive (pellets) was to have something else in the tank (that the bass could not kill) that would eat the pellets. In my case it was a small red-ear turtle. The bass watched the turtle eat the pellets and learned that they were food. I have tried it many times before and since without a turtle and the bass wouldn't touch the stuff.

Be careful, I was also only able to ever keep one bass in the tank at a time - they will eventually kill and/or eat eachother.

Once it gets bigger (10 - 13 inch range) try feeding it a mouse - very cool if you like that sort of thing. Hits it like a buzzbait then takes it down for the count.