If you would like to ask questions about pond management, call your local or district exrtension office.

Summer is usually the season of maximum pond use for recreation and aesthetic enjoyment. There are numerous events, both visible and invisible, that are occurring in the pond now. The warm water temperature means lower levels of dissolved oxygen. Couple this with a series of especially hot cloudy days and you could experience a fish kill due to insufficient oxygen.

The warm-up of the pond has also triggered fish spawning and the hatching (hopefully!) of thousands of fry (fish which still have a yolk sack). Largemouth bass spawned earlier in the season, but bluegill will spawn several times throughout the summer.

The combination of warm weather and sunshine means aquatic plants are growing. From single-celled algae to the higher order flowering plants, aquatic vegetation is important to the pond ecosystem. Single-celled algae, called phytoplankton, are the foundation for the complex food web. The submerged vascular plants oxygenate the water and provide cover for young fish, snails, and other animals.

Turtles are lining up on logs to sun themselves, their dark shells acting as heat absorbers. Like other reptiles, turtles breathe with lungs.

Human activity in the surrounding watershed and in the pond itself necessitates certain actions in order to maximize the use and enjoyment of the pond. A plunge into a pond on a hot summer day can be refreshing and enjoyable. In order to provide for the safety of all persons using the pond, provide a rescue station. At a minimum, it should consist of a life ring that can be thrown to someone in the water and a long pole that can be extended to a swimmer for him or her to grasp so that they can be pulled to shore. Be sure your family knows about water safety, how to swim, and how to call for emergency help using 911.

Discontinue the use of herbicides to control submerged weeds after early July. The combination of warm water and decomposing vegetation could result in a fish kill. Most seed producing submerged plants will have already done so. Little is gained by late season weed control. You can continue to treat algae with copper-based algaecides. You may want to consider partial pond treatments in an attempt to avoid the oxygen depletion problem associated with large quantities of decomposing weeds.

If you have further questions about your pond and how to care for it during the summer, contact your local County Extension Office.

If you have fish in your pond, the amount of dissolved oxygen (DO) in the water is an important characteristic. Fish need at least 4-5 ppm of DO to survive. This is usually not a problem, except when management practices or natural conditions result in a DO level that is insufficient, resulting in a fish kill.

The amount of DO in the water changes on a seasonal and daily basis. Warm water holds less DO than cold water. That means in the heat of the summer the DO level will be low. When you couple this with the decomposition of large quantities of aquatic vegetation, a process that extracts DO from the water, there may be an insufficient amount of DO to sustain fish, and a fish kill due to suffocation could be the result.

The amount of DO varies over the course of the day. During the daylight hours, aquatic plants are producing oxygen as a result of photosynthesis, and the fish are consuming oxygen. During the hours of darkness, the fish continue to breathe, but there is no oxygen production by the plants due to the absence of sunlight. So, on a 24-hour basis, the amount of DO begins to increase when the sun comes up, and continues to increase throughout the day. When the sun sets, the amount of DO decreases, and reaches its lowest level during the pre-dawn hours.

The pond management implication of this daily DO cycle is that if you have an aerator in your pond, the most critical time for its operation is the pre-dawn hours when the fish are consuming DO but the plants are not producing oxygen. Running an aerator for several hours, say 3:00 - 7:00 AM, will provide supplemental DO during the critical period.

Is the most expensive pond chemical for weed control always the best choice? What about the least expensive material? Will it work? Sometimes the pond owner has a choice between several chemical products. In addition to a cost comparison, the applicator should consider several other factors before selecting and using a chemical for pond weed control.

Several of the popular chemicals for pond weed control have some restrictions on fishing, swimming, or other uses of the water. Always read and follow the label directions!! The restrictions on a product may help the pond owner to decide which product to use.

A chart showing a cost comparison of numerous chemicals labeled for weed control will soon be available from the Northeast District Extension Office. If you would like to receive a copy of the chart, please send a self addressed, stamped envelope to Northeast District Extension, 1680 Madison Avenue, Wooster, OH 44691 and request "Pond Weed Control Economic Considerations."

This newsletter is edited by Larry Ault, District Ag & Natural Resources Extension Specialist - 330/263-3831. Editorial consultants are the following County Extension Agents - Mike Miller, Medina; Ernest Oelker, Stark/Summit; Barry Ward, Richland; Terry Beck, Wayne; Gary Comer, Logan and Eric Norland, OSU School of Natural Resources.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.