The Best Koi Pond Aerator Kit & Aeration System 2021 (updated)
Ponds with koi need oxygen, and one of the best ways to get plenty of it (and quickly) is with a dedicated aeration system designed for heavy fish stocks. In this article we cover our top aerator choices for koi ponds, with main considerations toward oxygen flow rate, energy saving potential, and ease of installation.
Should You Aerate Your Koi Pond?
All ponds require some level of dissolved oxygen in the water, even those without any koi or goldfish!
Oxygen is at the heart of every pond’s biological filtration system; a system where beneficial bacteria work to break down harmful organic waste substances, such as ammonia and nitrites. The reason oxygen is so important to this process is because beneficial bacteria are aerobic in nature, meaning they require a highly oxygenated environment to work efficiently. Even if you have a wildlife pond without any fish, the eco-system still requires some level of oxygen content to effectively process organic waste that sinks to the bottom over time. This constant breakdown of matter is what is known as the “nitrogen cycle“, a process essential to the biological filtration of waste in all natural bodies of water, including ponds and lakes.
If you have fish in your pond, such as ornamental koi, providing sufficient aeration becomes even more important, as your koi will need plenty of dissolved oxygen to breath. As well as this, koi produce huge amounts of waste which beneficial bacteria will need to break down continuously, and they’ll need that same oxygen content to carry out their job! What essential happens in a pond with low aeration is a battle for oxygen, with koi slowly suffocating and beneficial bacteria losing their ability to bio-filtrate, resulting in poor water quality and very unhappy carp.
The solution? If you have a heavy stocked koi pond you should consider adding a dedicated means of aeration! Even if your pond is well oxygenated most of the year, you could still encounter problems during times of naturally lower oxygen, and since you cannot ‘over aerate’ a fish pond, providing more oxygen has no real disadvantages to the eco-system. Good aeration will greatly improve koi health, water quality, and overall biological filtration, so it’s something we always recommend to new and veteran koi keepers.
The benefits of Aeration in Koi Ponds:
1) Improves Biological Filtration (Water Quality)
Extra aeration means more dissolved oxygen content will be available for beneficial bacteria to process waste. This will improve your ponds overall biological filtration and contribute to better long-term water quality for fish.
2) Promotes Happier and Healthier Koi
Koi can easily become stressed and sick in low oxygen conditions, and making sure your pond is well aerated ensures they have plenty of oxygen to thrive. More oxygen will help with a koi’s immune system, promote better color, and increase the rate of growth.
3) Ensures Safer Hibernation (Torpor) in Winter
During winter when a pond freezes over your fish may not be getting enough oxygen as top ice will prevent gas exchange taking place. This means harmful gases (Co2) can’t escape, and beneficial gases (O2) can’t enter the eco-system. Oxygenating water directly is one of the best ways to workaround this issue during colder months.
4) Discourages Parasites, Harmful Bacteria, and Pests
A final benefit is that a well aerated pond will discourage parasites, harmful bacteria, and even pests from calling it their home. These organisms thrive in stagnant, slow-moving water, so the more water flow and aeration you can provide, the better!
Can Koi Survive Without an Aerator or Air Pump?
Unlike wild carp in rivers and lakes, ornamental koi are completely reliant on the condition of their enclosed eco-system. If conditions are poor in one area, wild carp will simply migrate up/down river or to a different section of their lake habit where conditions are more desirable. Unfortunately, domesticated koi do not have this luxury, and they depend completely on us to ensure their environment is the best it can be for their survival and well-being.
Whether you need a dedicated aerator system would depend on your fish stock levels, the size of your pond, and how many natural aerators you’re currently running. Larger ponds with low fish stocks are unlikely to need a dedicated oxygen pump, especially if they have natural aerators, such as fountains and water falls. However, if you have a small-medium sized pond or your pond is heavy stocked with koi, providing more oxygen is always safer than assuming conditions are good enough. Once problems have already occurred due to low oxygen content, it can often be too late to reverse damage. This is especially true during winter and peak summer, where surface ice prevents gas exchange and extreme heat means water holds much less oxygen content.
Our opinion is that all heavy stocked fish ponds should have a dedicated oxygenator as a safeguard against water quality problems and to make koi more comfortable in their environment. Koi may be able to survive without one, but is it really worth risking the health of your fish to find out?
Koi Ponds in Winter – Why Aeration is Important
Regardless of your fish stocks, you should always try to provide some form of aeration to your pond over the winter season. This is because ponds easily freeze over for most of the western hemisphere, and a frozen pond prevents surface gas exchange taking place. This means that oxygen cannot dissolve into the water and harmful carbon dioxide cannot escape from the pond. As well as this, beneficial bacteria won’t be able to function without plenty of oxygen, so gradually harmful and smelly substances will build as oxygen content lowers. Eventually, aerobic oxygen-consuming bacteria will die and anaerobic carbon dioxide-consuming bacteria will begin to grow. This type of bacteria are bad for ponds, as they create a range of nasty by-products during decomposition, such as hydrogen sulphide. If you ever wondered why your pond smells a little like rotten eggs in Spring, it is likely caused by low oxygen conditions and the growth of slow-digesting anaerobic bacteria over winter.
Not only are dedicated aerators able to keep fish and bacteria happier during winter, they also help create surface movement, which prevents ice forming on the waters surface. If you combine a quality winter koi aerator with a koi de-icer, and you have a great combo for maximum aeration and oxygen during winterhibernation/torpor.
Koi Pond Aeration – Common Questions Answered
Q) How do I know if my koi pond needs extra aeration?
As a general rule, you cannot over aerate a koi pond – the more oxygen you can supply, the better! However, if you feel your pond is already well aerated, there are some things you can do to determine the possibility of oxygen problems in future. For starters, we recommend testing your pond water with a wide-range test kit (pictured), and taking note of ammonia and nitrite measurements. If these substances are higher than safe parameters, or close to them, it could indicate a growing problem with your biological filtration and beneficial bacteria. Low oxygen will cause bacteria to work less efficiently, so if your tests come back higher than average, providing more aeration may be helpful.
Another thing to look out for is the everyday behaviour of your koi in the pond. Are they gulping at the surface for air? Are any hiding? Are their color patterns strong? Are they eating their food when you feed them? A pond with low oxygen will cause koi to become stressed, and this will show in their behaviour and appearance. If you notice any of the above, or just a general change in behaviour, you can try to provide more oxygen to improve conditions.
On top of this, if you suffer with pests around your pond, such as mosquitoes, it usually indicates a low level of water aeration. Mosquitoes and other biting insects won’t lay their larvae in fast moving water, and instead prefer poorly aerated bodies of water. If the number of biting insects you experience rises in spring/summer, it may be time to boost the flow around your pond with an extra aeration unit.
Q) Solar Powered Koi Pond Aerators – Are they worth it?
Solar powered koi aerators have the potential to save you a lot of money in the long run, and they can be a very good investment depending on your situation. The problem with using solar power to aerate a koi pond is you’ll need to go big for the aeration to be worthwhile – and we mean BIG!
Most commercial solar aerators and air pumps are not designed for koi ponds; more so intended for water gardens between 50-500 gallons maximum. If you want to use solar power as your primary aeration source for a large pond, you’ll want to look for industrial sized aerators. These huge aerators (example pictured) are usually intended for lakes, but will also work for very large koi ponds so long as you get plenty of sunlight. They don’t require much in terms of set up, and there is no need for a mains socket connection so they can be installed remotely. Although the initial purchase cost can be high, you’ll have zero running costs over the pumps lifetime, potentially saving you a lot more money long term.
We’d still recommend an electric air compressor over a solar powered one for most koi ponds, as they’re cheaper to purchase and provide better reliability. However, if you’re in the market for a primary aerator for a remote pond, or to save money long term, a solar powered unit may be just what you’re looking for.
Q) What size aerator would be best for my pond?
Koi aerators are usually rated in Cubic Foot per Minute (CFM) and work to move air from a pressurised storage chamber using an air compressor. Unlike regular pond pumps that move water, air pumps work by converting potential energy (from electricity) into pressurised air which ends up in your pond as highly concentrated oxygen mix. Lower-end aerators may not always utilize a compressor, but higher-end models usually include one for better air flow and operation.
In terms of the size of air compressor you’d need for your pond, we’ve created a simple table to give you a rough estimate of the flow rates in CFM you may need. As well as the CFM, you need to also consider the air pumps maximum operational depth to ensure it can provide sufficient air flow at your ponds deepest point. This is usually indicated in the aerators product specification sheet, so be sure to cross-check this before investing!
| Koi Pond Size (US Gallons) | Recommended CFM Rating |
| 1000-4000 4000-8000 8000-16000 16000-32000 32000+ |
0.50 -0.80 CFM 0.80-1.20 CFM 1.20-2.00 CFM 2.00-4.00 CFM 4.00+ CFM |
The Best Koi Pond Aerator Kit Reviews 2021
Below are some of our top koi aerator recommendations, all of which have been chosen based on their flow rates, compression depths, and energy saving potential. Reviews have been included for pond air compressors suitable for small, medium, and large fish stocked ponds.
Best for Small-Medium Koi Ponds
1) AirMax KoiAir Aerator System Review
One of the strongest air pumps in our regular air pump article, and what we consider the best entry-level compressor for heavy stocked ponds, is the AirMax KoiAir Range! This low cost series of air pumps provide oxygenation support for ponds between 2,000 and 16,000 US gallons, and work by pumping air using a low energy and low noise air compressor system.
Due to the low purchase cost, these compact aerator pumps are ideal for smaller koi ponds or larger ponds with low fish stocks. The compressor is fairly powerful for it’s size, moving air at a rate of 0.80 CFM to a maximum of 1.70 CFM, depending on model. The diffusion method is with two highly porous cylinders attached to a backplate with mounting installation options. Oxygen is first compressed, and then pumped into the cylinders and diffused into your pond water.
The air flow is strong and will be able to provide a stable supply of oxygen to depths of up to 5 foot, but would work more efficiently at depths between 2-4 foot. Although these pumps wouldn’t be ideal for lakes or very deep ponds, they’re perfectly suited for most hobbyist koi ponds.
Unlike much stronger air compressors, this range also won’t break the bank, being able to work efficiently at extremely low wattage for good monthly energy savings. The pumps are also fairly quiet, although if the pond is close to your home you may want to consider installing a cover to further reduce operational noise. During winter it’ll run happily even in the coldest weather, and will provide much needed oxygen to fish under the ice and help prevent ice forming where the bubbles reach the surface water.
In terms of installation, it’s one of the easier pumps to get up and running thanks to its compact design and weighted air line and diffuser plates. The 3/8″ weighted air hose sinks by itself, and the diffuser plates are heavy enough to not be moved about by curious koi.
Although the air pump may be a little weak for the largest of ponds, it is a great entry-level aerator and will be able to provide a constant supply of oxygen to reasonable depths. The pump also comes with a 3 year warranty as standard for maximum peace of mind. Highly recommended for low stocked koi ponds or koi keepers on a budget!
- Design: Air Compressor
- Pond sizes: 2,000 – 16,000 US Gallons (depending on model)
- Max pond depth: 4 – 5 foot
- Flow Rate: 0.80 – 1.70 CFM (depending on model)
- Diffusion: Dual Diaphragm Plates
- Airline: 3/8″ – 10 foot length
- Warranty: 3 Years
Best for Large Koi Ponds
2) AirPro Koi Pond Aerator Kit Review
A big step up in terms of raw power, and suitable for large and extra deep ponds, is the AirPro Pond Aerator kit range. These piston powered 1/4 HP air compressors are capable of providing up to 2.3 CFM of flow rate, and can operate at depths ranging from 5-20 foot without much loss of pressure. They are ideal for water bodies up to 1 acre in size, or for large koi ponds up to 32,000 gallons in volume.
Larger than the KoiAir pumps, although still fairly compact, these powerful range of compressors are a great middle ground between entry-level and industrial-scale aerators. The pump is piston powered, and pushes compressed air down a weighted 3/8″ airline to a large diffuser plate which sits on the bottom of the pond. The diffuser plate is a single unit, but can still produce some serious airflow thanks to its large surface area. Installation is easy due to both the airline and diffusers weighted design, and the the pump is highly weather proof and environmentally safe as the system operates without running electricity through the water.
As this unit is able to provide such a high flow rate, it is extremely useful for winter aeration as it can also keep a large air hole open in the top ice. The surface movement it creates is energetic enough to prevent ice forming, whilst still retaining all general aeration benefits. If you have a large pond and plenty of koi, this would be a great choice as your over winter aerator.
Being a stronger compressor, it’ll be a little more expensive to run monthly compared to the KoiAir, but it’s still a very energy efficient pump in terms of the overall amp draw (1.7). It’s also a nosier than smaller pumps, but this should be expected from a stronger model with a higher compression rate.
Based on the volume of air flow and aeration AirPro compressors provide, they’re also useful for keeping away algae, duckweed, and mosquitoes – all of which prefer more stagnant conditions. It will also give your ponds beneficial bacteria a large boost productively, and ensure your koi have comfortable oxygen content in all areas of the pond.
Overall, a fantastic aerator kit which would be ideal as a winter koi aeration system, or as an all-year oxygenator for heavy stocked ponds. Especially ideal for for ponds over 8,000+ gallons, or particularly deep ponds or water gardens.
- Design: Air Compressor
- Pond sizes: 8,000 – 32,000 US Gallons (estimate)
- Max pond depth: 5-20 foot max
- Flow Rate: 2.3 CFM
- Diffusion: Weighted Plate Diffuser
- Airline: 3/8″ – 6 foot length
- Warranty: 2 Year (Compressor) & 5 Year (Diffuser/Airline)
Best for Massive Koi Ponds
3) AirMax SW/PS Koi Aeration System Review
Another offering from AirMax, but this time designed for much larger ponds, is the SW (shallow water) series and PS (deep water) series of air compressors. This flexible range of air pumps are optimized for both shallow and deeper koi ponds, being able to provide up to 5.8 CFM of air pressure to a max depth of 21 foot, depending on model. The shallow water SW pumps have been designed to work more efficiently at lower depths, producing fantastic aeration while consuming much less power. The deep water PS range is for use in very deep ponds and lakes, easily pushing oxygen to depths of 20+ foot with their up to 3/4 HP compressor engines.
We like this range of compressors as it offers huge flexibility for ponds of different sizes, depths, and koi stocks. If you’re wanting to get the very best aeration possible, and know the dimensions of your pond, you can be extra picky about getting the right aerator to match your specifications.
The powerful air compressor for both SW and PS series pumps comes housed in a custom built shelter, which mimics a natural rock formation. This cover protects against the rain, snow, and wind, whilst helping to block out noise from everyday operation. Included also is a built-in air filter for stopping debris from entering the chamber, which also helps maintain good circulation to prevent overheating.
Aeration is carried out through 3/8″ weighted air lines and a weighted dual cylinder aerator attached to a steel plate. The aerators are similar to the smaller KoiAir plates, but are larger in size and better optimized for operation under higher pressures. Depending on the model you choose, and the strength of compressor, you’ll get anywhere from 1 to 4 plate diffusers which are attached to the main pump.
For even more flexibility, both SW and PS series air compressors offer support for 115v and 230v lines, which can be helpful if you’re installing on a site with only one voltage option. The aerators are also extremely efficient in comparison with their CFM rating, with monthly costs running 24/7 ranging from as low as $10-$30, depending on model.
Installation is fairly easy, as the weighted plate and airline design allows fast sinking and pond placement. The compressors are much heavier than smaller models, but once they’re in place they’re super easy to maintain thanks to the great cover system which keeps cleaning to a minimum.
Although certainly overkill for smaller ponds, these aerators would be ideal for heavy stocked ponds, extra deep ponds, or particularly wide ponds with a lot of surface area to cover. The purchase price may seem a little high, but what you get for your money is some of the strongest and most efficient pond compressors available, with nice additional features for improving system longevity. If you want the best for your large koi pond or lake in terms of aeration potential, you really can’t beat the flexibility of the SW and PS AirMax range.