Do ponds REALLY need aerators? Here’s the truth

Last update:

Aeration is the process by which air is dissolved into water, providing any fish and plant life in water with the oxygen and carbon-dioxide levels they need to survive. However, ponds have survived millennia without aeration systems, so it leaves many to wonder, do ponds truly need aeration?

No pond needs an aerator. Shallow ponds can sustain life sufficiently without one. Deeper ponds do much better at sustaining a living ecosystem if there is a steady aeration system in place.

This article will dive into details about types of aerators, what they are used for, and how to keep an eye on your pond with no aeration system at all.

Surface Aeration

Surface aeration, unsurprisingly, is the best aeration for shallow ponds, since it mainly focuses on getting oxygen dissolved in the top, surface level of the pond.

Generally speaking, any type of device that stirs up water at the top level of a pond is going to be a surface aerator.

The most popular type of surface aerators is the fountain. Fountains are well-known, and well-liked, for their visually stimulating appearance and commonplace use in modern yards and gardens. Fountains are a great way to get water droplets into the air and back into the water with the newly dissolved oxygen.

Almost any type of fountain that can be integrated into a lake will be an effective surface aerator. Other types of surface level aerators are larger, heavy-duty equipment, more commonly used for large industrial sized ponds and lakes (such as fish hatcheries).

High-grade surface aeration equipment include low speed surface aerators, floating surface aerators, and paddlewheel aerators. However, unless you are planning to help sustain the ecosystem of a lake, it might be more beneficial to stick with fountains.

Fountains are not cheap but there are ways for you to save money. Check out our separate article on how to save money on pond fountains.

Bottom Diffusion

Bottom diffusion, also called subsurface aeration, are systems that do exactly what they sound like: they diffuse oxygen at the bottom of a pond or lake. Unlike surface aerators, which have a plethora of different types, bottom aerators generally have the same structure, with main difference between the types being ways they are powered.

Subsurface aeration systems use a compressor to pump air to the bottom of a pond, where the aeration system is located, so that the air (rich in oxygen and carbon-dioxide) can travel through the pond, top to bottom. In this way, the entire pond is likely to be sufficiently saturated in oxygen.

Bottom aerators can be up to ten times more effective than surface aerators, so if your pond still is having problems sustaining life even with a surface aerator, it might be time to consider getting a bottom diffuser.

Overall, while a pond can be a great addition to an already beautiful backyard, an aerator is not necessary. Simple, surface aerators (fountains) can prevent shallow ponds from dropping to low DO levels, but bottom diffusers and large surface aerators might be overkill for a garden pond with a few koi fish in it.

Aeration and Dissolved Oxygen

Ponds can be a highly active culture full of plants, fish, bacteria, algae, and other organisms, and all of these organisms depend on a steady level amount of oxygen dissolved into the water in order to survive.

Dissolved Oxygen (abbreviated “DO”) is the name for the level of oxygen dissolved in water. It is measured in parts per million (p/m), or milligrams per liter (mg/L) and for living creatures to survive in a body of water, the DO levels must be at 5 p/m or 5 mg/L at minimum.

Larger fish do much worse in low DO environments, unlike small fish, which can withstand DO levels to as low as 3 p/m.

DO is changed by a number of factors, and sunlight is one of the most important ones. For that reason, DO levels consistently spike during the day, since plant life in the pond can’t start producing oxygen until they have sunlight to use for photosynthesis. Because of this, DO levels can be critically low during the night or in early hours of the morning.

For more detailed information, you can check out this article written by the United States Department of Agriculture by clicking here.

No Aeration System

Aeration systems aren’t a required features for ponds. In some cases, your pond might be in a climate where it will naturally keep the DO levels high enough for its ecosystem.

Ponds in cooler climates will have a higher DO level than ponds in hot climates, because oxygen solubility (the oxygen’s ability to stay dissolved in a liquid, in this case, water) reduces as temperature increases. If you live in a colder climate, you can leave your pond as it is and check DO levels only as necessary.

Ponds with larger surface areas also have higher DO levels because sunlight directly hits more water, giving the plants plenty of fuel for photosynthesis. Larger surface area also makes it possible for more oxygen to dissolve into the water.

Equipment made to check DO levels (Dissolved Oxygen Meters) can be very expensive, running from around $90 to $3,000 dollars. Since not everyone has that kind of money, here are some things you can look out for to know if your pond has low DO levels:

  • The fish will spend more time at the surface of the water, usually breaking the surface to get some oxygen from the air
  • The pond’s water color will change from blue to brown or even black
  • The fish stop eating
  • The pond starts stinking like a rotten egg
  • The weather has been hot and cloudy (preventing direct sunlight from hitting your pond)
  • The weather has been extreme (heavy wind or rain)

If your pond has low DO levels, it might be time to get a surface aerator. However, shallow ponds likely won’t need one at all.

However, if you have your pond purely for visual appeal, getting an aerator won’t be as necessary. Aerators are more useful to people who are planning to use their pond to support an ecosystem (like those fancy people with koi in their yards), or people who are diving into the aquaculture industry (industry based around breeding and selling fish).

If your pond is more like a fountain, with mostly water and little to no life, an aerator won’t be useful whatsoever. The water will get brown and stinky overtime, but the easiest way to fix that is to refill it from time to time.

Photo of author


We always wanted a fountain of some kind at our house, but professional installation was just too pricey. So, we decided to make our own little fountain and after learning how, we thought we should share our experiences to help people in our same situation.

Leave a Comment