Pond Boss Forums AERATION Systems questions Winter aeration?

Answer - It depends. I depends mostly on pond temperature. Ponds in winter where water temperatures have dropped to 39F-42F will normally and naturally thermally destratisfy (mix top to bottom) which means that they are frequently, naturally circulating especially on windy days and cooler nights. Sometimes complete mixing daily. This is normally called spring turnover and it can last for weeks or a couple of months as long as the water is 39F to 50F. This natural destratification puts 100% oxygen saturated cold water on the bottom whenever destratificaion occurs. Then,, the high DO cold water usually lasts for weeks due to cold temps and low DO consumption by all almost dormant organisms in the pond. Dormant = very slow metabolism. The main exception will be is when the water is turbid and the pond is full of dead organics. Turbidity limits sunlight penetration and deep water photosynthesis (oxygenation) and the bacteria on the organics consume a lot of oxygen but not nearly as much when water is 39F-42F compared to when water is above 60F and approaching 80F+ when DO loss due to bacterial decomposition is highest and fastest.

In spring aeration start up, the more you allow the water temps to increase to above 50-55F the more likely you will have a larger amount of low DO develop on/above the pond bottom (deep above bottom water). But at 50-55F the pond is still occasionally top to bottom mixing (windy days). DO might start to be low right at the mud water interface after several warm days, surface temps near 70F and turbid water. But at 50-55F the low DO water will not be enough volume right above the bottom sediment that it cannot be blended with the high volume of good water on top and not cause any fish stress problems. Hydrogen sulfide (H2S poison gas) forms only after DO is lost / absent. Also when water is 50F-55F on top it has a real high amount or large volume of water that is saturated with DO. This high volume (depth) of high DO water has a very large buffering capacity to a low or small volume of low DO water. Plus respiration of all things in the pond (bacteria - fish) is still pretty slow in the 50-55F cool water. Cool water holds much more DO at 55F than water at 80F+. Water holds more DO and DO lasts longer at temps of 50-55F and lower than at 80F+.

Fish stress problems at aeration start up are due to a large volume of water above the bottom that has lost DO and as a result, as time passes is accumulating large amounts of hydrogen sulfide (H2S -fish poison). Moving all this high volume in a thick layer (2-6ft thick) of bad no DO water with H2S dissolved gas to the surface to significantly dilute the surface layer is where start up aeration becomes a problem. This feature primarily begins to happen once the surface water reaches 60-70F+. The rule is: the warmer the surface water and the longer it has been warm the more likely DO will be low in high volume on the bottom.

Was this too confusing and involved to understand for the lay person?