How deep is your pond, and how deep is your deep diffuser? You can run aeration during the heat of summer if you are able to maintain a thermocline, where cooler, less oxygenated water exists. They cant live there, but they can escape the heat temporarily.

Get yourself a pool thermometer and a removable weight. Take readings from about 16" deep, again at half the depth of the pond and then at the deepest area. If you're finding a significant variance in temps from top to bottom, then you may be ok, if that coolest water is conducive to WE.

If your summer diffuser is set on the bottom at depth, you may need to elevate it on a platform, relocate it shallower, or you may have to switch to running an early morning schedule (4am-10am). That too depends on how long it takes to turn your pond over with one diffuser.

.10 surface acre pond, 10.5 foot deep. SW LA. The epitome of a mutt pond. BG, LMB, GSF, RES, BH, Warmouth, Longear Sunfish, Gambusia,Mud Minnows, Crappie, and now shiners!!...I subscribe!!