To slow the Air One Plus down simply add a bypass valve off of the manifold and exhaust off some pressure.cfm's. This will allow your amp draw to be less $$ than turning the valves down and creating more back pressure. Additional back pressure on that particular compressor will not shorten the life as with your short tubing runs and depth it is hardly working. Just over sized for what you want to accomplish. Consider running it 24/7 but slower. As Bill mentions every pond has a BOD, It normally increases as a pond ages. The key to aeration is to try to size to the potential maximum BOD and always keep the DO supply over the demand. This can be difficult with bloom crashes, plant/ algae organic matter rapidly decomposing from natural or man made causes.