I am going to suggest two different things:
1) Go for something other than the bullheads. Flatheads are hard to come by and snail bullheads (in my experience) have all been in tough places to sample. They have been in deep, fast-flowing water with large boulders that they can hide underneath. So maybe trapping for young ones would be best?
Instead, look into fish that get large (hopefully large enough to not temp the redbreast to eat it) like bluehead chubs (Nocomis leptocephalus
) or even the creek chub (Semotilus atromaculatus
). The blueheads are great aquarium specimens. They grow fairly fast when young, they are active and very fun to watch. The creek chubs (I have never personally had one) can get pretty large and have bigger mouths than the blueheads. They also have an appetite to go with it (so an small fishes would be at risk of being eaten). These species are easy to find/catch than the snail or flat bullheads.
2) Go with more redbreasts or other sunfish. While I have been too cautious (or scared
) to try this method, it has been suggested on this forum to try another approach. While I cannot pull up the exact thread, one of our members and a reputable native fish breeder with a specialization in sunfishes - Brian Zimmerman, has had success with keeping large aggressive sunfish in groups. Rather than only having 2-3 sunfish in a 55 gallon tank, allowing them to develop territories and defend them aggressively, this method suggests more like 5-6 or so sunnies in the same tank. The idea is that the sunfish will constantly be in close proximity to one another and will not have the space/energy to develop and defend territories.
However, if you go this route, use caution with male/female ratios. I don't have enough experience to expand, and I am not sure if this method requires an all-male tank or not. Good luck.