So if I'm understanding everything that's been said, the real key is in the diffuser. If it's equipped with a check valve that prevents back pressure the pump can operate sufficiently even with lower CFM?

The unit/kit I'm leaning toward says it's rated to operate up to 30 feet deep at .8cfm. It comes with two rubber membrane diffusers (The tube shaped kind) equipped with a check valve, mounted on a plate and 50ft of sinking 3/8 hose. The pump itself is a 1/8 hp rotary vain/diaphragm design.

.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!!