It would work great for the Bullhead!
For the minnows...not so much...
You're not going to produce an ecosystem in 100-gallons that produces a self-replicating food supply for a foot-long catfish, except possibly as the source of an occasional snack or treat. That's just not enough space to expect a colony of minnows to evade and elude the cat. At night, when the minnows are dormant, the cat likely won't be and will gradually...or quickly!...catch and eat them.
Bullheads aren't picky eaters. You certainly don't need to feed them live food.