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Aquaculture / Fisheries - "Center of Excellence"

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Aerators and circulators can provide several substantial benefits to ponds, but they can be quite expensive and they are not always necessary. Below are several situations where the investment in an aerator or circulator can be justified.
Situations where aerators or circulators are worth it:
- If you plan to fertilize, feed regularly, and/or heavily stock fish
- If you plan to pursue trophy-sized fish with aggressive management strategies
- If your pond is accumulating large amounts of organic material (muck)
- If your pond has a history of severe turnovers and oxygen-related fish kills
- If you want to improve the aesthetics (water fountains) 
Photo of vertical pump aerator
In general, aerators and circulators can allow you to grow more pounds of fish per volume of water than you could naturally. If you are already satisfied with your pond's fish production and do not have substantial risks of oxygen depletion or organic material accumulation, then aeration is not necessary. You can learn more about identifying risk factors by visiting the Fish Kill page. 

Oxygen does not easily dissolve into water, and water holds far less oxygen than the same volume of air. While atmospheric oxygen does naturally dissolve into water, the process is very slow and only occurs where atmosphere and water interact. The easiest way to increase the rate of oxygen transfer is to increase the area where atmosphere and water are interacting, by agitating the water. Natural agitation comes in the form of wave-action from wind. When wind creates waves, the surface area of the water increases, which increases the rate of oxygen transfer into the water. Additionally, the energy stored in the waves that is released when they splash into the bank or hard surfaces creates small areas of turbulence below the surface that helps transport oxygen deeper into the water. Aerators are specifically designed to agitate/oxygenate large volumes of water. Circulators are specifically designed to propel large volumes of water. Some models combine aeration and circulation simultaneously. The best aerator/circulator for your situation depends on your needs, the physical characteristics of your pond (especially depth), your budget, aesthetic preferences, and more. The appropriate size and location of aerators also varies greatly from pond to pond. In general, the typical fishing pond can be sufficiently aerated with 0.5 to 1.0 HP per surface acre. Because there are so many variables at play when selecting an aerator, it is best to contact the aerator manufacturer for guidance and sizing estimates. A partial list of aerator providers is included at the bottom of this page. For more detailed explanations of dissolved oxygen dynamics, aerator efficiency, and other considerations, refer to the Additional Resources linked at the bottom of this page. Below are examples of the general types of aerators and circulators. 

Diagram of a water fountain

Water fountains are usually floating devices that propel water several feet into the air. Fountains provide some aeration but usually only at the surface and a modest distance around the fountain. Fountains are popular additions to golf course ponds, city park ponds, and urban ponds where aesthetics is deemed more important than aeration. If aeration is your primary concern, other aerator types are more effective. Fountains are typically located in a central location in clear sight of the most common viewing angles of the pond.
Diagram of a vertical pump aerator

Vertical pump aerators use a submerged motor and propeller to lift a dome of water a short distance into the air. Like fountains, vertical pumps are usually mounted to floats that can be secured in place by wires or ropes connected to anchoring devices at the pond bottom. Vertical pumps create good surface agitation with good aeration efficiency. They are viable options in fairly shallow ponds because they can operate in shallow water, but they also only aerate surface water and a modest distance around the pump. Vertical pumps are good choices for shallow ponds where surface aeration is the primary concern. Vertical pumps are typically centrally located and evenly distributed around a pond to ensure complete coverage of oxygenated water.

Diagram of a paddle wheel aerator

Paddle wheels are the aerator of choice for most pond aquaculture operations because they add more oxygen per dollar of electricity than other types of aerator in relatively shallow ponds. They consist of a motor mounted to a floating platform with a large rotating drum or cylinder ringed with broad metal or plastic flaps that splash into the water and lift it into the air. Paddle wheels operate at fairly high RPM's and they can create considerable circulation at the surface which helps distribute the oxygenated water to other parts of the pond. In rectangular ponds, a single powerful paddle wheel can be located on one of the long banks facing straight across the pond towards the other long bank to create two areas of circulation which can keep the entire pond aerated. While highly effective, paddle wheel aerators are typically expensive, heavy, and not considered one of the more attractive options in aeration/circulation.

Diagram of a circulator

Circulators are designed to move large volumes of water. Some aspirated models inject bubbles into the moving water to accomplish both aeration and circulation. Circulators can come in floating and submersible models with motors that turn boat-like propellers below the surface. The angle of the propeller can be adjusted to fit the depth and circulation needs of the pond. Submersible models can be mounted to the legs of fishing piers, boat docks, stumps, or beneath floating platforms. Circulators are particularly helpful in preventing thermal stratification in ponds, which can reduce or eliminate annual turnovers altogether, and forcing oxygen down to deeper parts of the pond.

Diagram of a diffuser
Diffusers consist of air blowers mounted on land near the pond filling air hoses connected to bubble diffuser pads anchored to the pond bottom. The diffuser pads release a stream of small bubbles that release oxygen and create vertical current as they rise. Diffusers are the most effective tool for aerating and circulating deep water (10+ feet deep). The drawback to diffusers is that they are not very effective in water less than about 8 to 10 feet deep. Diffusers are excellent options for preventing thermal stratification in deep ponds and reducing the threat of annual turnovers. It is common for one air blower to supply air to several diffusers distributed around the pond for complete circulation and aeration. Solar and wind-powered diffusers are available. Solar models feature solar panels and some have batteries allowing them to operate at night. Wind models include large windmill towers. The wind models work only when the wind is blowing. Solar and wind-powered diffusers are good options if electricity is not available at the pond site and they are free to operate after equipment purchase and installation plus regular maintenance, but they are not as powerful or effective as their hard-wired counterparts. Diffusers are most effective when operated continuously, and the solar and wind-powered diffusers typically go offline when the aeration is needed most (at night and when the wind is not blowing).

Additional resources:
NRCS AEN-3 Aeration of Ponds Used in Aquaculture
SRAC 3700 Pond Aeration
Aerator Manufacturers List (Publicly sourced information, listed companies not endorsed)

What to read next:
Fish Kills