So I have a few questions, and forgive my ignorance on the subject. Is the reason that a pond's temp increases with aeration related to the outside air temperature due to the location of the compressor? (i.e. If your compressor is outside in 90-degree air, it's sending 90-degree air into the water, which is what causes the water to heat up.) If yes, would the opposite also be true, if the compressor is in a climate-controlled room, which could potentially send cooler air into the water?
The water tends to heat up due the the added exposure to the sun and ambient air temps. This is because the water is constantly being turned over bringing cooler water up and allowing it to "soak up" the heat. Eventually, you heat up the entire column of water. Some heating occurs due to the hot compressor air, but I am betting its negligible compared to the power of the sun and air temps.
BUT, there is a thing called evaporation cooling. So, depending on the humidity reading in the ambient air, wouldn't aerating also possibly cool the pond as the air that is pushed to the bottom of the pond absorbs moisture from the pond on it's way to the surface?
QA, have you tried the jar test to see if the clay turbidity is due to electrical inbalance or mechanical means? If you had a denser phytoplankton bloom (18" -24" visibility and none of that due to clay turbidity) I think your O2 levels would be higher in the daytime and therefore when you ran the aerator at night you would have higher O2 levels overall than what you have now.
I would be interested to see what the O2 levels (and temp levels) would be if you ran the system 24/7 for a week. If you felt the water was getting too warm you could shut the system off and the water at the bottom of the pond would start cooling off pretty quickly due to the cooler soil temps surrounding the pond.
