To aerate or not...Is it really a question?
Scott Schillig
Scott Schillig

For the past year, you’ve planned construction of your new pond, and now it is complete. The dirt guys did what they do, you’ve created the perfect environment of habitat for your precious fish to reach your goals. With a couple of prayers and a timely rain dance, it’s filling with water. Now you begin to think about aeration. Do I need to aerate? What type of aeration do I need? Go to the hardware store, buy a pump and shoot water straight up? Is it as simple as putting some air bubbles in the pond or is there more that to think about?

Those are some of the questions asked on the Pond Boss Forum and here is a primer on types of aeration, when it’s needed, and what it accomplishes.

You don’t “need” to aerate your pond. BUT, a properly designed and installed aeration system will greatly slow down the eutrophication process, help prevent summer and winter fish kills and prolong the life of your pond. The key phrase here is, “properly designed and installed." If you are looking at numbers of fish in a pond, a “properly” aerated pond can hold twice the amount of fish that a non-aerated pond can hold.

There are basically two types of aeration: surface aeration and bottom diffusion aeration. Surface aeration can be broken down into further into the three more categories of fountains and surface agitators, and circulators. Bottom diffusion systems can be broken down into three different categories as well: grid based or electrically operated, solar operated, and windmill or wind driven systems.

Surface aeration is primarily used in shallower ponds, or in areas of a larger pond shallow enough that a thermocline is less likely, which is typically between 6 to 10 feet deep, depending on the individual body of water. Fountains, volcanos, paddle wheel, and PTO driven agitators are used to throw water into the air are typically used in shallow ponds.

Volcano Agitator

Paddle Wheel-type agitator


PTO-driven agitator

Fountains are used both for display and to aerate shallow bodies of water, volcanos are more for adding oxygen to the water and less for aesthetics and paddlewheels/PTO driven agitators are more for aquaculture production ponds.

Bottom diffusion aerator by Vertex

Bottom diffusion aeration systems are typically used in deeper ponds, where a thermocline will set up, usually deeper than 6 to 10 feet. They are used to bring the low oxygen bearing water to the surface so it can absorb oxygen from the atmosphere.  In terms of energy efficiency, where applicable, bottom diffusion aeration systems will give you more bang for the buck, i.e. move more water for less dollars per hour operating expense.

Wind operated systems
These systems are either windmill or some type of floating turbine system on the pond. The good thing about these systems is that once the initial expense of purchasing the system is done, the only added dollars are maintenance costs. The compressors (in my experience) need to be rebuilt every 2-4 years, and to do that you either need to tip the windmill tower over to get the compressor to the ground, or climb the tower and work in the air. If the system is floating on the pond, then you just need to bring it up onto the shore to work on it. These systems are not high volume air producers, only a couple CFM (cubic feet per minute). These systems only work when the wind is blowing, and if there are trees or other obstructions in the way, they should be mounted higher than the obstruction.

Solar Systems
Like the name says, they are driven by the sun and use solar panels to collect energy which is converted to electricity. Some have batteries that allow them to operate at night, some don’t. They can be put far from any available electricity, but the panels have to see the sun to operate, and in the winter in colder climates they have to be kept free of snow. They can produce more CFM than a wind driven system, and are the only option for ponds that do not see a lot of wind and are far from any grid based electricity.

Grid-based or electric systems
There are many different manufacturers, all with different or multiple compressor types. Rocking piston, diaphragm and rotary vane compressors are the choices. Grid bases systems have the capability of pumping the most air and wherever electricity is available, I prefer to use this type system. It won’t stop working because the wind isn’t blowing, nor will it stop working if the sun doesn’t shine for a week or two at a time. The compressors do have to be rebuilt from time to time, but depending on the type of compressor the rebuild interval could be 2-3 years or over 10 years. The key is to furnish them with clean air, keep them well ventilated and use the appropriately sized wire to bring power to the compressor.

Bottom diffuser systems work by disrupting the thermocline, destratifying the pond. That allows the aerobic bacteria to work on any decaying matter faster, which helps minimize muck build up, and it allows the fish to utilize the whole water column in the pond during the summer, not just the oxygenated water near the surface.

How do I know the system is properly designed for the size and depth of pond that I have?

What you are looking for is a system that will move the volume of water in your pond to the surface at least once every 24 hours, twice is even better. Don’t overdo it; too much air could cause the pond to be turbid. You want to know how many CFM the compressor is producing at the depth the diffusers are placed, and you also want to know how many GPM (gallons per minute) of water the diffusers are moving. If the company that is making the components for a DIY system, or the complete system cannot tell you that information, keep looking. The compressor should be able to produce the amount of air that you need to move the amount of water you need to move. A rule of thumb to remember is that for every foot of water depth that the diffuser is placed at, you need 0.5 psi to get air to that diffuser. So, a diffuser in 15 feet of water needs a minimum of 7.5 psi of air in enough CFM of air to properly operate that diffuser.

Do I need to aerate in winter if the pond freezes over?

Two inches of cloudy ice or two inches of snow will stop most of the light getting to the water. So, the phytoplankton in the pond cannot produce oxygen, and the living organisms in the pond will slowly consume all the available oxygen. The biggest fish will die first, followed by smaller and smaller fish. That is known as winterkill. By having a bottom diffuser placed no deeper than 1/3 the total pond depth (and close enough to shore that anything that goes into the water can walk back out without climbing up on the ice) to keep an area open that is approximately 10% of the total pond surface, you will prevent most if not all winterkill problems.

Should I run my aeration system at night, during the day or both?

I recommend running the system 24/7. If you want to run the system less than that, make sure the system is large enough to move the correct amount of water per 24 hr period. i.e. if you want to run the system 12 hr a day, then the system has to move twice the amount of water that a system that is designed to run 24 hr a day. If you only want to run the aeration system part of the day, the lowest oxygen levels typically occur right before sunrise, so I would plan on the hours of operation to include the few hours before sunrise and at least an hour or two after sunrise.

For any other questions, go to the Pond Boss Forum, sign up and ask away!!

Scott Schillig
Hoosier Pond Pros
Grovertown, Indiana

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