Pond Aerators can be a game changer in restoring balance to a problematic waterway suffering from poor water quality.
The key to keeping a healthy a pond or lake is aeration; this is done by simply moving water from below the surface up to the surface in mass volume. Any pond that doesn’t have adequate aeration will inevitably have problems. The types of problems a poorly managed pond can experience are unchecked plant and algae growth, foul odors, and fish kills.
Background on Stormwater Pond Design
In Florida, most of the ponds and lakes in residential and commercial developments are designed stormwater systems. Simply put, a stormwater system is a tool for managing the runoff from rainfall. When rainwater lands on rooftops, parking lots, streets, driveways and other surfaces that water cannot go through, the runoff (called stormwater runoff) flows into grates, swales or ditches located around your neighborhood. These send the water into your stormwater pond. A stormwater pond is specifically designed to help prevent flooding and remove pollutants from the water before it can drain into the groundwater — our main source of drinking water — or into streams, rivers, lakes, wetlands, or estuaries.
Detention systems (ponds) are the most recognizable stormwater system. They are designed to allow material to settle and be absorbed. After a storm, water slowly drains from the pond through a pipe in the “outflow” structure. Part of the pond, known as the permanent pool, is always below the level of the drain structure.
Without a stormwater system, the stormwater runoff usually flows into the nearest water body without treatment. The runoff carries pollutants such as litter, motor oil, gasoline, fertilizers, pesticides, pet wastes, sediments and anything else that can float, dissolve or be swept away by moving water.
So that stormwater pond behind your house or adjacent to your business is essentially nothing more than an “aquatic trash can”, collecting the “trash” from runoff before it can discharge into a receiving waterway. The primary treatment mechanism within a wet detention pond is sedimentation. Many of the nutrients and metals removed from the water column settle and accumulate in the top few inches of the pond bottom sediments.
Herein lies the rub: over time, these contaminants can have a detrimental effect on the water quality within your stormwater pond. Fertilizers and organic debris (muck) accumulate providing an internal nutrient load of Phosphorus and Nitrogen within the stormwater pond.
OK, so you’ve got an “aquatic trash can” and its full of “trash”. What should you do?
Well, there’s some good news. Most stormwater ponds in Florida are permitted and designed as “aerobic” systems. They’re typically designed with the objective of maintaining aerobic conditions within the water column.
Stratification and Its Effect
While your pond may have been designed as an aerobic system, in reality this might not be what is occurring. Environmental conditions, such as sunlight, temperature, rain, and wind, can lead to a stratified pond. Stratification is the separation of the water column into layers based on temperature, oxygen level and density. The water column separates into a layer of warm, oxygen-rich water (the epilimnion) at the surface, a dividing layer (the thermocline), and cold, oxygen-poor water (the hypolimnion) near the bottom. The lower layer of the pond can be anoxic. Under anoxic conditions, nutrient release from sediments occurs at a much faster rate than what would occur under oxic conditions. Nutrient release from bottom sediments can fuel explosive algae growth, including harmful algae blooms and lead to poor water quality.
What can you do?
Restoring aerobic conditions to the entire water column, including the bottom layer which interacts with sediment, can be achieved by installing a pond aerator system. The most common type of pond aerator system is the “bottom diffused air” system. A pond aerator system consists of three components: A cabinet with an air compressor, weighted tubing, and a diffuser head. Air is pumped by the compressor, through the tubing, and then released from the diffuser head which is located at the bottom of the pond. As the air rises from the diffuser head, water is lifted by bubbles, and the movement of the rising water creates circulating currents within the waterway.
It’s important to note that the actual bubbles only add a minimal amount of oxygen to the pond. The main source of aeration in any pond is water contact with the atmosphere. But the pond aeration system induces circulation and mixing, causing the bottom anoxic layer to rise to the surface where it can become oxygenated. In time, a pond aerator system will cause the whole water column to become evenly aerated and de-stratified.
As an added bonus, added benefits of aeration include:
- Increased fish habitat
- Decreased chances of a “turn-over” event
- Aerobic conditions for digestive bacteria (anaerobes), which can consume the bottom sediment!
Want to learn more?
Here’s some helpful resources to read through:
Maintaining Dissolved Oxygen Levels in Your Pond to Reduce Fish Kills – UF | IFAS NW District
The Role of Aeration in Pond Management – UF | IFAS
Plant Management in Florida Waters: Dissolved Oxygen – UF | IFAS
Aeration, Circulation, and Fountains – Clemson Extension
