This is the time of the year that pond owners are most likely to experience “oxygen depletion” or a lack of oxygen in their ponds. Large numbers of fish can quickly start dying when the dissolved oxygen level in pond water drops too low. Unfortunately, it is normally the largest fish that die first when we have low oxygen problems.

Several factors can lead to low oxygen problems. First of all, pond water temperatures are unusually warm with the record daytime temperatures and very warm nights. The oxygen level of water naturally drops as the water temperature rises. Secondly, with the lack of rainfall, many ponds have low water levels which increases oxygen problems. A third factor is stormy weather. Summer thunderstorms can cause a condition referred to as “pond turnover.” This causes the different layers of water in ponds to mix together and results in quick oxygen level drops.

The bottom line is to watch for oxygen depletion problems if you have a pond. The best way to check for low oxygen in a pond is to go out early in the morning and look for large numbers of fish up near the water surface. Large numbers of fish at the surface, at or soon after dawn, indicate a lack of dissolved oxygen in the water.

Call the Extension Office for more information about dealing with oxygen depletion in ponds.

Norman Edwards is coordinator of Walker County Extension Service.