PINE BLUFF -- Aeration systems provide benefits to pond water quality, fish production capacity, fish kill prevention, suppression of some aquatic weed species and prolongation of the pond's lifespan, Scott Jones, Extension small impoundment specialist, Department of Aquaculture and Fisheries at the University of Arkansas at Pine Bluff, said. Pond owners often question whether they should operate their aerators during winter months.
"Generally, it is beneficial to operate aeration systems all year in Arkansas," Jones said. "For Arkansas, however, winter is usually the season where aeration provides the least benefit. Electricity costs to run grid-powered motors or compressors, wear and tear on parts that need routine service or replacement and super-cooling of deep water, particularly when using diffused aeration systems, are considerations owners should weigh."
Diffused aeration systems are designed to push streams of bubbles from the bottom of the pond to the surface, creating circulation and injecting oxygen throughout. This circulation prevents thermal layers from developing, he said. Water is most dense at about 39°F. Water warmer or cooler than that will rise to or stay near the surface.
"This is why we see layers of cooler water near the bottom during summer and 'warmer' water near the bottom during hard winters -- especially if ice forms at the surface," Jones said.
Warm-water fish stocked in most Arkansas ponds use the slightly warmer bottom layer as refuge during the coldest parts of winter. If a diffuser keeps the pond fully mixed during winter, water can continue cooling below 39°F, he said. While the risk of freezing a pond solid is not realistic, further reduction of temperatures can increase stress on warm-water fish species, slightly increasing the risk of mortality and fungal infection, especially in catfish.
"Pond owners with diffused aeration systems can move their diffuser pads to shallow water, 25 to 50% of the max depth of the pond or run only a portion of their shallower pads while deeper pads are turned off," Jones said. "Or, the system can be deactivated completely for the winter to mitigate or eliminate super-cooling deep water."
Most aeration systems -- diffusers, fountains, surface pumps, paddle wheels and circulators -- will help prevent ponds from developing surface ice, or at least keep a small area near the aerator ice-free, he said. In colder climates where ponds may have weeks to months of ice and snow cover, maintaining openings in the ice is an important management practice to prevent "winter kill" from low dissolved oxygen and harmful gas build-up below the ice.
"Arkansas rarely experiences prolonged or thick enough ice cover to justify ice mitigation practices," he said.
During periods of hard freezing temperatures, fountains and surface aerators should either be run continuously or removed from the pond completely. Operating these aerators occasionally on timers or leaving them in the pond deactivated could allow them to freeze and sustain damage.
While moving, adjusting or removing aerators for winter, take the time to perform scheduled maintenance according to manufacturer recommendations, he said. Filters need regular inspection and replacement, and motors need periodic maintenance to keep them running at full efficiency.
"Winter aeration is beneficial to Arkansas ponds with some minor adjustments and considerations from your warm-weather setup," Jones said. "But you will not be missing much if you want to save some electricity and wear and tear by deactivating your system until spring."
For more information about pond aeration, contact Jones at 870-575-8185 or [email protected].