Crappies would wipe out your bullhead problem in a few years, but then you would have a crappie problem.
I think the best answer is to stock one or two large blue cats and wait for them to do their work.
I wonder if the blue cats you stocked were really bullheads. Just a guess, but possible.
It is also possible that the upper ponds have an in-check population of bullheads.
Eventually, big bass will wipe out the bullheads if you let nature take its course.
That's my 2 cents
