Keep the water clean and he'll eventually come around, let him be even for a couple of weeks, basses dont need to eat for like weeks at a time! When they're ready to chow they will. With a good environment and proper aeration he'll destress overtime. Imagine going from vastness to confinement, it takes a bit of time. G'luck!
Btw keep a box of worms in the beer fridge, and try around day break (not everyday though), remember it hunted for food not too long ago meals came randomly, it'll get hungry sooner or later. Keep us updated ^^