Joe, Im surprised you do not have the inwater check valves as I have not seen these stones without them even when a check valve is on the intake airfilter.They may no longer be blue in color and appear to be a 3/4 inch coupler sometimes instead of a check valve. Rotary vanes build extreme pressure (30-40psi) when they have to clear the airline of water on startup with out these check valves, This is a heavy load for bearings and starter switches until the pressure is back down to normal operating pressure (5-10 psi) Perhaps you are bleeding off on startup and slowly putting the air to the diffusers which will work also.As far as the smaller pond if you have 4 of any type of diffuser in that small of body it is probably well aerated.You are right about the self cleaning aspect of rubber membrane diffusers and their ability to self clean by "flexing" and then returning or rebounding to normal operating pressure. Mineral deposits are no longer a concern. There are a few different types of rubber membranes on the market. Some have limitations on the amount of cfm you can apply to them so they do not stretch and lose the builtin check valve function.When looking at diffusers of any type the total length of run of tubing (friction loss) should be considered also.Some membrane diffusers cause more backpressure than others.Even though they will have the same water pressure on them at the same comparative depth (approx 1 lb per 2 ft of depth)If concerned about spring startup try running 1-2 hours the first day and doubling your run time each day until you are at 24/7 (4-5 days) when the air temps( and top water ) averages 45-50 F minimum,This is a conservative startup procedure but one that works well vs going straight to 24/7. Ted