One of the main limiting factors to aquatic life is dissolved oxygen. In commercial fish production, supplemental aeration is almost always required to sustain large enough crops to keep the farm profitable. Most private fishing ponds are not stocked or pushed to produce fish heavy enough to need supplemental aeration, Scott Jones, small impoundment Extension specialist at the University of Arkansas at Pine Bluff.
“A properly sized aeration system is one of the most beneficial investments one can make to their pond,” Jones said. “The primary benefits are insurance against oxygen depletion especially during annual turnovers and increasing – sometimes doubling – the fish carrying capacity of the pond. Other benefits include unlocking the entire water column for fish production rather than just the shallow areas, helping natural microbes continue processing organic wastes year-round, which reduces muck and nutrient accumulation, and even suppressing certain aquatic weeds and nuisance algae.”
In cooler climates, aerators can also maintain an opening in the ice during winter to maintain gas exchange with the atmosphere to prevent “winter kill,” he said.
Fountains
The most visually satisfying aeration type is the surface fountain aerator, Jones said. These are floating motors that propel streams or cones of water several feet into the air. While in the air, each water droplet absorbs oxygen and expels waste gases before falling back into the pond.
“The zone of influence for fountains can be fairly small and usually only affects surface conditions around the aerator to a couple feet deep,” he said. “Some models come with adjustable tubes that draw water from near the pond bottom. These models can have a larger impact as they pull cool oxygen-deficient water from the bottom rather than just shuffling around already oxygenated surface water. This type of aerator is generally best when aesthetics are equally or more important than aeration. Some manufacturers offer color-changing lighting kits that create a stunning nighttime visual.”
Vertical Pumps
One of the best options for aerating water shallower than about six feet is vertical pumps, Jones said. They feature a floatation device with an electric motor and a propeller submerged below.
“The propeller thrusts water into the air in a broad dome that aerates and creates good surface agitation for several feet around the aerator. They can usually operate in as little as about 2 feet without disturbing the bottom and muddying the water,” he said. “While not as aesthetic as fountains, vertical pumps provide more oxygen transfer into the water per dollar of electricity than fountains and you can still order lighting kits from some manufacturers to get cool visuals and very good surface aeration.”
Paddle Wheel
The aerator of choice for commercial fish producers is usually paddle wheel aerators because they provide the highest rate of oxygen transfer for shallow ponds with good surface water circulation, Jones said. An electric motor mounted to a floating structure spins a drum or shaft covered in rows of plates that splash water into the air.
“These aerators are typically large, noisy and can be expensive to operate depending on their horsepower rating and setup, which reduces their appeal for most recreational uses,” he said. “Most who use this type of aerator only operate them when supplemental oxygen is needed, usually from about midnight to a couple hours after sunrise, which reduces their daily operation cost in comparison with a continuously operating system.”
There are tractor PTO versions of paddle wheels that can be used in emergencies by simply backing the device into the ailing pond and leaving the tractor running until the oxygen issue has been resolved. While recreational pond owners will usually favor other options, those curious about commercial fish production in shallow ponds should consider paddlewheels.
Diffusers
Diffused aeration features an air compressor mounted on shore pushing air through weighted hoses to bubble diffusers located on the pond bottom, Jones said. As bubbles rise to the surface, they give off oxygen, absorb waste gases and create vertical current that draws deep water to the surface.
“This type of aeration becomes more efficient with smaller bubbles and deeper diffuser pad deployment,” he said. “Generally, 6-8 feet is the minimum depth recommended for using diffused aeration, though it can still work in shallower ponds with more expensive multi-diffuser pad systems.”
Diffused aeration can prevent thermal stratification and is the best at aerating deep water compared to other aerator types. Manufacturers typically size these aerators such that they can circulate the entire pond volume about once every 24 hours, Jones said. It is generally best to operate diffused aeration systems continuously during the warm season, but some will operate them on timers to reduce electricity use.
“Be aware, though, that activating diffused aeration in a pond that is already stratified during summer can cause a turnover and fish kill,” he said. “It is best to follow the startup schedule of day one, run it for 30 minutes, then turn it off for the rest of the day. Day two, run one hour. Day three, run two hours. Day four, run four hours. Continue doubling the run time each day until you are running continuously. Most other aeration systems do not need to take this precaution and startup schedule because they do not break thermal stratification like diffusers will.”
Circulators
Owners of very small ponds (less than ½ acre) who are not interested in fountains, the noise and surface agitation of vertical pumps and paddlewheels, or who lack the water depth for optimal diffused aeration, may consider circulators, Jones said.
“These are submerged electric motors turning propellers that push water away from a mountable structure, like a dock. They can move a good deal of water, keep small areas free of certain weeds and prevent ice-over during winter,” he said. “While circulators do not aerate, they can suppress stratification and help push oxygenated surface water towards the bottom in smaller ponds. The area of influence depends on how powerful the device is, up to about 150-200 feet laterally and 6-8 feet deep for a 1 hp unit.”
Propeller Aspirators
A variation on circulators, propeller aspirators are floating or mounted motors with a submerged propeller on a hollow shaft that draws air from the surface to the vacuum of the spinning propeller creating a stream of bubbles and current away from the device, Jones said.
This type of aerator/circulator can be quite efficient in terms of oxygen transfer per unit of electricity. Some manufacturers have designs that are fully submerged to maintain a natural appearance to the pond.
“Like circulators, the depth and area of influence are limited to about 50-200 feet away from the device and up to 6-8 feet deep depending on the power and setup of the motor,” he said. “This type of aerator is popular in industrial and municipal wastewater treatment facilities, commercial fish production, and is a viable option for fishing ponds where other alternatives are not acceptable or desirable.”
General Information
The source of electricity is an important factor in aeration systems, Jones said. Until recently, only systems that were supplied by the main power grid were able to provide reliable aeration when it’s needed most, at night and during calm hot cloudy conditions.
Renewable energy sources tend to underperform or go offline during these priority periods making them more novelty than legitimate options, he said. However, with rapid improvements in battery technology, solar and wind-powered systems are now becoming legitimate primary aeration options.
“If you decide to use renewable energy, prefer units that can provide at least 24 hours of battery back-up. Circulators, vertical pumps, propeller aspirators, paddlewheels and fountains will all need power fairly close to shore,” Jones said. “The price for increasing power cable lengths can be tremendous. For diffused aeration systems, air hose is far cheaper than power cable. Mounting the compressor at the nearest power source and running up to hundreds of feet of air hose to the pond can save money versus burying power cables down to the pond.”
Due to the tremendous range of options and variables at play it is difficult to provide hard-fast price estimates on aeration, he said. From reputable manufacturers, anticipate at minimum $1,500 for aeration systems suitable for small ponds (<½ acre), and $2,000-3,000+ for systems large enough to aerate 1-2 acre ponds. The price increases as pond size increases.
While sticker shock is real on these systems, owners must consider the potential financial loss from a major fish kill and subsequent restock or draining and excavation of organic muck accumulation after struggling to fend of nuisance algae blooms or aquatic weeds, Jones said.
“It’s not only how much money it will cost to restock/rebuild, but also the two to four plus years it will take to grow those restocked fish into adults large enough to provide satisfaction,” he said. “For many, time is money. The appropriate type and size of an aeration system can grant you more quality pond and fishing time than you may be able to easily quantify financially.”
For more information about pond aeration, contact Jones at (870) 575-8185 or joness@uapb.edu. For assistance with Fish Health and water quality issues, contact UAPB AQFI Extension labs and supervisors: Dr. Grace Ramena, director of the UAPB Fish Health Diagnostic Lab and Fish Health Inspection Lab at Lonoke, at (870) 575-8137 or ramenag@uapb.edu; or Travis Collins, Extension associate for the Lake Village/Eudora Fish Health Diagnostic Lab, at (870) 355-7007 or collinst@uapb.edu.
The University of Arkansas at Pine Bluff offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.
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