September 28, 2021
Fall Pond Aeration: Why It’s Important
Why aeration in autumn is essential to a healthy pond.
Fall pond aeration is important in many circumstances. Sudden drops in temperature, a reduction in sunlight, strong storms, and an increase in organic debris all contribute to a reduction in oxygen levels that directly impact the health of the pond.
Reduction in oxygen from plants
Aquatic plants, due to photosynthesis, create oxygen for ponds. Naturally, as the cold sets in and there is less sunlight, algae and other aquatic plants start to die off or go dormant. The green plants that survive produce much less oxygen because of the reduction in sunlight.
Increase in organic matter
Organic debris is most prevalent in the fall. As leaves change color and drop to the ground, they and other dying aquatic vegetation are swept into the pond. Fertilizer and decaying insects/animals also find their way into the water, further impacting the water composition. Nature uses beneficial microorganisms (aerobic bacteria)—which require oxygen to live and thrive—to decompose organic matter. With the influx of debris in the pond, more oxygen is needed to speed up decomposition. If there is not sufficient oxygen, the organic matter will be slow to decompose and can build up at the bottom of the pond. Not only will this make for a major spring cleanup, but the condition can also contribute to fish kill in the winter.
Pond turnover
During summertime, without proper water circulation, ponds will settle into three layers—known as thermal stratification. The top layer (epilimnion) is the warmer water near the surface. The bottom layer (hypolimnion) is the cooler water at the bottom. The layer in between is the metalimnion. Within the metalimnion is a horizontal plane called the thermocline—the point of sudden temperature change. If you have ever jumped into a lake or pond and felt an instant difference in temperature, you passed through the thermocline.
As temperatures drop, the warmer water at the top of the pond increases in density and sinks to the bottom. Eventually, with the addition of windy days, the pond will mix, and the temperature will become more consistent throughout. The biggest concern is a sudden drop in temperature or a major storm that turns the pond over suddenly. If this happens, anoxic (anaerobic) water at the bottom of the pond can mix throughout the water column and deplete oxygen levels leading to fish kill. Turnover can also make the pond cloudy and smelly.
Benefits of subsurface aeration
Bottom diffused aeration increases dissolved oxygen levels, helping to offset the reduction in oxygen from plants. Aeration allows beneficial aerobic bacteria to multiply, speeding up the consumption of organic matter that has accumulated in the pond. Subsurface aeration also circulates water to make temperatures and oxygen levels more consistent at all depths—preventing the devastating effects of sudden turnover.
Year-long pond aeration is recommended for best results. If you need help selecting the right size pump, check out our pump sizing article: What Size Air Pump Should I Buy?
If you have any questions, please give us a call or send an email.
Phone: 734-944-5032
Email: info@hiblow-usa.com
Author: Mike Miner
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