bc - Greg G. considering where he is in the south may need to run their aerators 24/7, BUT we in OH very rarely need to do that. I have never tested circulation patterns and mixing frequency in areas other than in Ohio. You can run aerators 24/7 in OH but it is definately not needed in most ponds. Exceptions occur. I consider 24/7 run times in our area a waste of electricity and it causes premature wear out of the compressor vanes and bearings especially when the extra run time does not provide anything more than that of a daily 5 to 8 hr mixing.
With 4+ cfm and two diffusers running in a northern, 3/4 acre, fairly normal, shaped pond you can thourghly mix it in 5 to 8 hrs running time. Guaranteed. Double your money back if I am wrong. I and others in my area have proven this many, many times and verified it often with oxygen & temperature tests throughout the summer. The important thing is to adequately size the unit for your pond in the first place. Don't undersize it and it will mix and destratify your pond quickly and efficiently.
Get a good unit adequately sized for your pond and put it on a timer and run it at night or during the day when you are not there. Rotary vane compressors are barely noiser than a loud hum. If no noise is a real important issue place the compressor in shed or garage and run the air delivery line to the pond from the compressor location. (Which is the way I always recommend one doit if at all possible.) Outside shelters tend to be more maintenance and "messing around" in our winters. We can push air 1000 ft if the tubing is sized properly.
