Pond Turnovers Causing Fish Kills Possible During Summer Season

During the hot summer months, farm pond owners often face the frustrating prospect of losing some of their fish population to oxygen depletion in the water.

Hot Springs, Ark. – During the hot summer months, farm pond owners often face the frustrating prospect of losing some of their fish population to oxygen depletion in the water. The event – referred to as a “turnover” – is a phenomenon that is largely unavoidable. 

Pond turnovers are a result of changes in water properties.  Caused by changing temperatures in surface waters, brought on by the progression of the seasons, it is a common scenario around this time of year.

In the spring, the water in a farm pond is cool and mixed, with a uniform temperature from the surface to the bottom of the pond. As spring turns to summer, surface water temperatures warm rapidly and the summer breezes are generally light and do not mix the pond’s water from top to bottom.  The surface of the water may be near 90 degrees, while the temperature at the bottom could be 20 degrees lower.  Additionally, the oxygen levels in the cool, bottom layer of water may have decreased drastically because of the breakdown of organic materials in the pond. 

A sudden afternoon thunderstorm, bringing strong winds and heavy rains, can cause enough force to mix a pond’s water from top to bottom.  The cool, oxygen-deficient bottom layer is abruptly mixed with the surface layer, causing severe oxygen depletion throughout the pond. This commonly results in a pond full of dead fish.  Most people do not realize their pond has turned over unless there is a fish kill. 

After a turnover occurs, aeration of the water is key.  Aeration can be accomplished by adding water that contains oxygen, by splashing pond water into the air so that oxygen enters the water or by adding air to the pond water (bubbles).  For best results, use a large pump with a screened inlet to spray water back into the pond. 

If a massive fish loss occurs due to a turnover, pond owners should restock the pond with small fish and start over. They should also fertilize the pond, as fertilization revitalizes the plankton bloom and recovers appropriate oxygen levels.  A good grade of fertilizer with elevated phosphorus levels works well. Examples of standard formulations are 10-20-10 or 18-46-0.  

For more information on pond management, contact Jimmy Driggers at the Garland County Extension Office, 501-623-6841 or email jdriggers@uada.edu.    

EHC Information

Would you be interested in joining an existing Extension Homemakers Club? How about forming a club in your community?  EHC is the largest volunteer organization in the state. For more information about how you can be involved in EHC in Garland County, call 623-6841 or email me at jvincent@uada.edu.

4-H Information

If you’re between the ages of 5 and 19, you can join 4-H! We have a club for you, or you and a group of friends can organize a club of your own.  For more information on the 4-H program call the Extension office at 623-6841 or 922-4703 or email lbates@uada.edu . 

Master Gardener Information

If you have an interest in gardening of any type, or would like to learn more in the horticulture field, the monthly Master Gardener meetings are open to the public and guests are always welcome. For information call the Extension office at 623-6841 or 922-4703 or email abates@uada.edu. 

The Arkansas Cooperative Extension Service is an equal opportunity institution.

By Allen Bates
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture

Media Contact: Allen Bates
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
236 Woodbine Hot Springs AR 71901
(501) 623-6841
abates@uada.edu

The Arkansas Cooperative Extension Service is an equal opportunity institution. If you require a reasonable accommodation to participate or need materials in another format, please contact your County Extension office (or other appropriate office) as soon as possible. Dial 711 for Arkansas Relay.

Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.