Meadowlark, to adjust the flow to each diffuser, we use a thermal temp. gun. Grainger carries one for about $100. By adjusting the flow so each valve is around 5 deg. of the other valves, the flow is pretty even then. The only other option is to place a cfm flow meter on each valve, but at $50-$100 each, it is too expensive.
Bugermeister, the only true way to tell if you are reaping the full potential of your system is to test with an O2 probe. Seeing what is happening at the surface is like a poloroid snap shop or a doctor saying you look okay without doing a blood test.
If you must run your system in intervals, the times you are running it are the best. Keep in mind, most compressors are designed to run continously and not on and off. It takes a lot for the compressor to push that air down initially and if there is no way to stop the water from entering the air line, it must push that out too through the diffuser.
The compressor is like a plane taking off. It is full throttle until it reaches altitude, but then it backs off for the remainder of the flight.
Okay, enough analogies.
