FWIW, surprisingly, I haven't encountered too many problems with bullheads in ponds with established LMB populations. They are just SOOOOOO susceptible to predation when they are young. If the water is relatively clear, and the vegetation is relatively under control the LMB will hammer them into submission. The very few that survive will grow huge and actually taste great. I'd tend to resist the urge to renovate, in particular if you think that it may happen again.
