Thank you both for the replies!

1.I have not fertilized or used any chemicals recently but it’s possible the neighboring farm did. I think a big part of the runoff came from a farm behind my pond. It’s been dry since I bought the place 5 years ago, but there is a clearly obvious place where water has flowed before that heads towards my pond.

2. 3 acres, 6ft avg depth. Yes all of the water was retained and the pond was about 6 feet lower than when I bought it. It rose about 4 feet in one night.

3. Water test before but not since. “Ultra pure” was what the test called it.

4. Some floating foam/scum is the only thing I have noticed. Water seems to be un-muddying too, going back to normal.

My aerator pump was just replaced so it’s working great. It might be slightly undersized. Have never had a fish kill before and it’s been a lot hotter in years past than so far this year.

Should I not run the aerator 24/7 when it’s hot? I was under the impression that once you get to 24/7 that it should stay that way forever. That’s how it’s been for 4 years.

Thanks again!