Pond Boss Forums GENERAL QUESTIONS Water chemistry water surface temps

My 2 acre pond is only about 10-101/2 ft deep in the deep end. Shallow end about 4-5 ft deep. Yesterday air temp hit 100. Water surface was 95 at 2:00 pm. This morning at 8:00 am surface temp was 89. Is this normal for a pond or small body of water? How dangerous is it. I do not have aeriation. I am familiar with large body of water temps. I still see fry in the very shallow water on the bank edge. Fish are still feeding good on the auto feeders.

Without aeration, the surface temp, and top few inches of water can change a considerable amount throughout a day. Sunlight on dark colored bottoms absorb heat also. The fish will hover near, even slightly in, the thermocline when water gets too warm.

There IS a danger, but several variables play into just how much danger there is for a fish kill.

Warm water holds less dissolved oxygen than cooler water, but in a "small" BOW, the colder water below the thermocline has probably had all the oxygen consumed and has become anoxic, and filled with toxic gasses. If this is the case, the fish will not go into the cooler bottom water, or at most, enter very briefly. Unless your pond has so many fish that the fish consume more oxygen in the upper water than gets dissolved and circulated through the air/water interface, you should be fine. If fish are seen "piping", gulping air at the surface, it indicates very low dissolved oxygen is available, and fish are suffocating. If seen, put a boat motor, or brush hog into the water to agitate heavily for emergency aeration.

Fry consume very little oxygen, so it's not unusual to still see them even in low DO situations. The fact your fish are still "feeding well" is a sign DO is adequate.

It might be a good idea to cut back feed amounts some to lessen Biological Oxygen Demand (BOD) as a safety measure in excessive air temps. Also, if you have a good size algae bloom (Deep green fertile color), A few cloudy days could kill that oxygen producing algae, and cause a big increase in BOD during the decay, causing an oxygen crash.