Answer: Turnover is generally in the spring or fall. It’s created by a blending of low oxygen and medium range oxygen. So if you can picture in the summertime, the bottom of the lake is going to have low oxygen issues because of lack of bacteria activity, lack of sunlight. And the top layer of the pond is going to have what will support fish. Well, if you end up with a temperature, ambient temperature variance or a rainfall event that the water from the rain changes the temperature, you’ll lose that thermocline zone. When you lose the thermocline zone, the bottom of the pond and the top of the pond water blend and that blend dilutes the oxygen level.