Nat, I think Greg makes an excellent point-larger blue cats are excellent predators, and would probably thrive while controlling the 'gill population. Todd Overton sells blue fingerlings, or if you want to jump start things, you could add a few larger blues along with your channels. It might make the fishery a little more interesting to have a few really large blues around...someone around here caught a 90 pound blue out of a 2.5 acre pay lake a couple of years ago, they estimated that it had been in the lake for 15 years, as none larger than 20 lbs had ever been stocked.
You could still have an excellent put and take fishery with channels being the mainstay as well.
