What Kind of Aeration System is Right for my Pond?

Finding the Best Aeration System for Your Pond

Finding an aeration system for a pond is often a complex process, and it can be difficult to decide which is best for your specific ecosystem. Here, we’ll walk you through the various types of pond aeration to help you make a better, more well-informed purchasing decision.

Aeration of Large Ponds

This section is for those with large ponds.

Though pond aeration occurs naturally, an additional pond aerator is often required to ensure the long-term health of your fish, as well as the entire pond ecosystem. But the right kind of aeration system for your pond comes down to two critical factors:

  • The pond’s average depth
  • The primary function of your centerpiece

Lack of aeration causes your pond to stratify, and form layers in the water; typically these layers are at different temperatures with different levels of oxygen. The top of the pond can become stagnant and full of muck. 

Also, muck will accumulate at the bottom of the pond unless there is proper aeration, and it will become shallower over time. Plants in your pond, including algae, need oxygen to decompose. 

And if they don’t get enough oxygen, the old plants will decompose faster than the new ones, sending up noxious gas bubbles from the bottom. A pond aerator system will de-stratify your pond and result in less chance of a fish kill and bad forms of algae and other noxious weeds. 

You don't want your pond to look like this photo.

 Pond Scum Image


 Fish Kill Image

Common Aeration Systems for Ponds

Basically, there are two different ways to aerate: from the top of the water and from the bottom. Whether to get a surface aerator or a bottom aerator or both depends on the two factors we highlighted above. (Depth and function.)

Surface Aeration

Aerating from the surface is the most common. A float sits on your pond, usually black to blend in the water, and a pump is attached to the underside of the float. The float allows the whole unit to rise and fall with the water levels. But what kind of water flow and thus aeration you get depends on which kind of surface aeration you choose.

Decorative Surface Aeration

The most common type of surface aeration is the use of a decorative fountain. A nozzle sits on the float attached to the pump. The display can be quite dramatic and complex with several angled holes--or be simple. A decorative fountain pump will use an impeller. 

The idea of a decorative fountain is to focus on decoration first and aeration secondarily. Kasco Marine recommends a 2 to 1 ratio: for every surface acre of pond, use 2HP of decorative fountain. 

And Kasco concentrates on aeration for ALL of their fountains. For some other brands, we would recommend up to 5HP of fountain for each acre to be aerated. Fountains that push the water high into the air and wide typically do so by shrinking the size of holes in the nozzle. Thus, with these kinds of fountains, pond aeration is decreased.

Aerating Fountain Aeration

 V-shaped aerating fountain

An aerating fountain will provide more aeration than a decorative pond fountain. That’s because instead of an impeller, the pump will use a propeller. 

Also, the “nozzle” is basically a large hole, which provides only the V-shaped pattern. Kasco recommends a 1.5 to 1 ratio. 1.5 HP pump for every surface acre of the pond.

Plain Surface Aerators

 A solar surface aerator 

There is one other kind of surface aerator, and this one provides the most aeration of all, probably double what a decorative fountain will do. A propeller is used for surface aerators, too, but there is no nozzle at all, and thus no restriction to water output. There is also little display, just large splashing bubbles. Kasco Marine recommends a 1-to-1 ratio for surface aerators.

Bottom Aeration Using Diffusers

The thing is, if your pond is deep, with an average of over 7 feet, bottom aeration works best. An air compressor is located at the shore, and a hose carries the air to a diffuser unit at the bottom of the pond. Though compressors used to be rather loud, nowadays, they are much quieter. 

They are also very energy-efficient, and a great deal of aeration can be done with a quarter-horsepower compressor. They need to be housed to protect them from the elements, thus quieting them more. 

If your pond is shaped conventionally, as a rectangle or oval, then it’s often the case you will only need a single diffuser at the bottom of the pond. If it has islands or unusual shapes, there’s a good chance you will need to place more than one diffuser at the bottom. 

We really think the Kasco pond aerator system is the best bottom aeration on the market.

kasco diffuser  


Combining the Two Kinds of Pond Aeration

If you have a deep pond but still want to see a fountain, you can combine the two types of aerators. A pond aeration system could use a surface fountain for the display and agitation of water below, and the diffuser system would properly increase dissolved oxygen levels. The fountain would not need to aerate as much and could focus on beauty. This focus allows for a greater range of prices as well as a dramatic viewpoint.

You can add lights to any of the surface aerators, even pure aerators.

Aeration for Small, Backyard Ponds

This section is for aerating those with small, backyard ponds, usually with koi. Even in small ponds, fish and the pond ecosystem need oxygen year-round. Oxygen can be added to the water in several ways.

Waterfall and Streams

My personal favorite type of aeration system for a pond has always been the waterfall and stream combination. These keep the water moving and reduce stagnation, all the while adding oxygen to the water. They also are terrifically easy to build, much easier than making the pond. Building a pond necessitates a lot of digging, leveling, and placement of boulders or flagstones around the edges.

But the extra dirt you have from digging the pond can be used to build a waterfall! First, you make your mound, which can be quite short or really tall, depending on how much height you want. Remember, taller spillways do make more sound, but at the same time, they can cause more splash, potentially leaking outside the pond. It is best to use some large boulders around the spillway to decrease the splash outside of the pond.

Spillways can be made with flagstone, which is easy to break into smaller parts, or you can buy acrylic spillways to fit between boulders.

You will need to decide how many spillways you want. Is it a one-tier waterfall, two-tier, or even more?

Once you’ve created the shape of your waterfall, you really should place underlayment below the liner. It is tempting to use concrete, but it almost always cracks. You can always cover the liner with concrete if you prefer a concrete look.

Try to choose rocks of various colors and textures. Rearrange them until you find the right look. You can also add driftwood or other ornamentation.

A stream can be formed simply by trenching a shallow ditch going to your waterfall. Again, cover with liner and underlayment. Streams are often prettier if small stones, like Mexican pebble, cover the liner.

Small Fountains

Small pond fountains also will aerate the pond, but remember to constantly keep the wind in mind. Nozzles with tiny holes in them will often plug up, and the water droplets can be so slight that the water can easily drift outside of your pond. 


Carefully adding plants will also not only beautify your pond but also add to oxygen levels and provide shade for koi.

Sub-surface Aeration

Another way to add oxygen to your pond is by placing a diffuser in it. A small compressor is located outside the pond, and tubing is connected to it and connected to a diffuser that sits on the bottom of your pond. The diffuser will have a number of holes in it, out of which columns of air bubbles rise to the pond’s surface.

Aeration Systems for Ponds Recap

Ponds NEED oxygen to sustain a healthy balance. There are several ways to utilize an aeration system for your pond, which will help your fish and the entire pond ecosystem. And remember, do NOT add more fish than the size of your pond can handle.

Don't forget the aesthetic value of lights!

If you want to make sure your small or large pond lasts longer than most, check out our pond aerators!

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