OK thanks for the info.

Is the warm water bad for fish just because of the temperature? Or is it because warm water carries less oxygen than cold water?

I was thinking that using the aerator would be helpful because even though it makes the water warmer it should also increase the oxygen level.

Other posts have mentioned watching out for bad smell when you first start up the aerator, but the pond smells normal to me. Does that mean it's less likely to cause problems?

The aerator manual says to start out at 30 mins on day #1; then go up to 1/2/4/8/16/24 hours on each subsequent day. Is that too rapid of a change? So far I have noticed no fish deaths.