Often in the hottest part of summer only the top few feet of water have sufficient DO. If you get a big cold rain the pond will mix/turnover and none of the water will have enough, DO. It only takes a few minutes of very low DO to kill fish. This is exacerbated by ponds with at/near carrying capacity loads of fish as they have high DO demands.

Last edited by ewest; 08/01/22 10:59 AM.