I get asked questions every week about the difference between fountains and diffused aerators.  They are very different, and aerate in a different way, so it often matters which one you choose. Many people use the words "fountain" and "aerator" interchangeably, however, these two types of pond equipment are not the same.

Fountains are meant to improve the look of the pond and aerate the surface of the pond and up to 6’ in depth. They spray up 15 feet into the air depending on the model, horsepower and spray a desired pattern. Fountains are the focal point in ponds and lakes. Fountains mix and move the water and increase oxygen levels on the surface, but areas far away from the fountain and deeper areas of the pond will remain stagnant.

If you’re concerned with the health of your fish, introducing more oxygen into the pond with a sub-surface diffused aerator would be what you would want to consider installing. Both units require an electrical connection, although a sub-surface aerator uses an air pump that is placed outside the pond.

So, if you have an existing electrical set up then you will need to find a unit that is compatible with the current voltage available. For example, if you have 115V electricity then you will want to look for a 115V unit, if you have 230v then you will need a 230v unit.


Floating pond Fountains plug in directly at the electric source; the cable runs out to a float where the water sprays up from the center. There are eye hooks on the float in order to anchor the float in place.

This type of fountain floats on the surface of the pond and shoots water up into the air to creating beautiful displays, and lights can attach to the float to enhance viewing at night.  Fountains can truly enhance and beautify a pond or lake and cancel out noise from traffic, while infusing some air into the pond creating aeration.  Another benefit is that these units are good at forcing floating debris, algae, and plants like duckweed to the shores edge where they can be more easily removed or treated.

Decorative pond fountains won’t aerate the whole pond surface or depth. Aerating the water refers to the mixing and agitation of surface water or the infusion of atmospheric oxygen into the water column.  So technically, fountains do aerate the pond at the volume of a diffused aeration system.  

The difference is in the method in which they do it and their effectiveness in doing so.  Aerating fountains have been the management method of fish hatcheries worldwide for over half a century.  This equipment aerates the water column, while also keeping your fish happy and healthy.

For the best management results these fountain units are best installed for ponds that are 6 feet or less.  Fountains only use the water in the diameter of where they are placed, so you are only mixing the water within the first 5-6 feet of water depth.  For systems deeper than 4-5ft and larger than 7000 square feet you will need a diffused aeration system in addition to the floating fountain.


Unlike the decorative floating fountains, bottom diffused aerators have two lines that come off of the air pump (an electrical wire and an airline). The other major difference is that an aerator diffuser air pump is an external pump that site next to the electrical sources and the diffuser rests on the pond floor instead of floating on the surface. 

So it is important to have your electric source near the pond. The other line is the airline that runs from the pump into the pond, and down to the diffuser that sits on the pond floor. The airline is usually weighted and lays along the floor of the pond.

Sub-surface diffused aeration systems use an air compressor pump, airline, and diffusers. The diffusers rest on the bottom of the pond and “diffuse” billions of bubbles which rise to the surface of the pond.  The size of the pond will determine how many diffusers you will need to effectively turn over the pond.

Diffused air does more than just inject oxygen into the water, it also removes harmful dissolved gasses such as methane, ammonia, nitrous oxide, and sulfur dioxide. As the oxygen moves out of the bubbles and into the water, these harmful gases move in and are carried to the surface where they are blown away by the wind.  

The bubbles will grab all of the water around them and lift it to the surface.  This efficiently turns the pond over and exposes the nutrient rich water from the bottom to the atmosphere, releasing even more harmful gases and turning in more air.  

Diffused air systems are necessary for the degradation and decomposition of organic soft sediment, because they provide tons and tons of tiny oxygen bubbles to the bottom sediments, creating a great environment for the bugs and microbes to consume the organic material.  

So in conclusion, if you are looking to turn some water and have a beautiful display, a fountain is the way to go.

If you are looking to foster an aquatic ecosystem and help the overall health and longevity of a pond, then a diffused aeration system is the right option.

If you desire both, then install them together and enjoy your pond for years to come!