The bullhead won't purposely seek out to destroy your plants. As it looks for a place to hide or to get to food .It will push through,behind and around your plants uprooting them. So use plants the have good roots,that aren't fragile, and plant sparsely. Some native plants I have kept with bullhead have been Elodea Canadensis,Cabomba,Valisneria, and Sagittaria subulata.
Their are many smaller native fish that alot of people don't know of. When most people think native they think sunfish,bass, and catfish. But what about the many different and colorful darters,dace,shiners,and madtoms. Most of these can be kept in a twenty gallon tank.