TIMELY TOPICS
Ponds are a popular landscape feature many enjoy. Spring is the time to initiate a number of pond management practices necessary to achieve desired outcomes later this summer. Ponds can have a range of environmental benefits but some pond management goals can conflict with one another. The best approaches to management depend on the priority goals of the pond owner. Most folks with ponds have expectations for water clarity, freedom from algae and weeds, and the ability of the pond to support fish.
One of the most common problems for ponds is excessive algae. Right now is the time to implement an algae control program. Copper-based products are generally effective at controlling algae but it is important to initiate these treatments now, according to label directions, well before algae begins to appear in early summer.
Another attribute to check for pond health is alkalinity. Alkalinity can be measured with test kits used for swimming pools and spas. The goal is to achieve an alkalinity of above 20 parts per million and below 100 ppm. Alkalinity is increased by the application of agricultural lime across the entire service of the pond. Do not use quicklime, hydrated lime, or slaked lime as these react much too quickly in the water and can result in fish kills.
Pond weeds other than algae can be controlled with herbicides labeled specifically for aquatic applications but it is essential to correctly identify the plant to ensure a particular herbicide will be effective and apply the herbicide at a time that will be most effective in that weed’s life cycle.
Fish benefit most from a diverse environment with some algae and plants present. It is unrealistic to expect pond waters to be clear like a swimming pool and still support fish and other aquatic life. An Extension agent colleague taught me fish prefer a pond that is “pea-soup-green.” While preventing excessive buildup of nutrients in ponds is important, there are circumstances where application of fertilizer to ponds can benefit fish populations by increasing growth of beneficial plants and algae. But alkalinity must first be above 20 ppm in order to realize a benefit from the fertilizer. Ideally, storm water run-off is impounded above the fishery pond to prevent indiscriminate amounts of sediment and nutrients from being flushed into the fishery pond.
Aeration is another beneficial component of a fishery pond. In high summer heat, the upper layers of a pond can become quite warm and deoxygenated with the fish existing in a lower, cooler, more oxygenated layer close to the bottom of the pond. Sudden disturbance of these layers such as can happen with a heavy storm can cause these layers to “flip,” resulting in a fish kill. Submerged aeration devices can help ensure the entire pond is adequately oxygenated to support the fish i n t he p ond. S urface fountains are generally less effective at thoroughly oxygenating a pond.
Some excellent printed resources on pond management area are available at the Rockbridge Extension Office located on the second floor of the Rockbridge County Administrative Building at 150 S. Main St., Lexington.
