Choosing the Best Size Pond Fountain or Aerator For Your Pond

Ponds need aeration in order to stay healthy for fish and other animals as well as plant life. Ponds become stratified (layered) when there is not enough aeration, usually with the coldest layers at the bottom and the warmest layers on the top, resulting in too much algae and pond muck. If there is not enough dissolved oxygen in the pond, you could encounter a fish kill. Your pond can start to stink, too. Plants, including algae, need oxygen in order to decompose. If there is not enough pond aeration, old plants will decompose faster than new ones, and the muck sends up gas bubbles which can create noxious odors. and the buildup of muck. Your pond will become ugly and unpleasant as shown above. 

Surface Aeration versus Bottom Aeration

Surface Aeration

Most people are familiar with surface aeration. You’ve seen pictures, no doubt, of the enormous fountain at the White House. The action is occurring at the surface of a small pond. Though that fountain might be stationary, most surface aeration for ponds consists of a floating fountain design.

In this design, a pump is suspended by a float, typically black to blend into the water. When the water level lowers, the float falls with the water level. When the water level rises, the float rises with it. To keep it in place ropes are attached to the float and are either attached to cinder blocks or other weights at the bottom of the pond or tied to the shoreline.

Three Kinds of Surface Aeration

Display (Decorative) Fountains

Display Fountains offer the most dramatic displays. These fountains use an impeller inside the pump and typically offer multiple display patterns. Kasco recommends a two-horsepower per each surface acre ratio for optimal aeration when using display fountains. For a half-acre pond, Kasco recommends a one-horsepower pump. The ratio is 2 to one. Note, however, that these recommendations are for Kasco units, which are independently tested. Other manufacturers often require more horsepower per unit for proper aeration, and a lot depends on the nozzles, which restrict flow.


Display Fountain by Kasco
Kasco with Mighty Oak Nozzle

Pump with impeller

Aerating Fountains

Aerating Fountains use a propeller instead of a pump impeller, and are more efficient than decorative fountains. There is only one pattern, the V-pattern.  Kasco recommends a 1.5 to 1HP ratio. For every one acre of pond surface, a 1.5 HP unit should be used. Again, these are Kasco specifications, and only provide a rough estimate for other companies.

Aerating Fountain by Kasco at night

A pump with propeller

Surface Aerators

Surface Aerators also use a propeller, but provide the most aeration of all surface aeration systems, double of what a decorative fountain will do. There is no nozzle, thus no restriction to water output. There is also little display, just large splashing bubbles. At night with lights they are still pretty.

Kasco Aerator with lights

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. Compressers vary in noise, though the Kasco units are relatively quiet if properly housed. 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 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.


Bottom aeration, bubbles rise from bottom
Compressor for Kasco Aerator
Kasco diffuser with cabinet to protect the compressor

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

Sizing Your Pond

For surface aeration, you only need to know length x width.
Length x Width divided by 43,560 = total surface acreage. Thus, for a 200 foot by 100 foot pond:

200 x 100 divided by 43,560 = .459 surface acres

If you are using bottom aeration, you need to calculate total gallons or acre feet of water in your pond. You need to know Length x Width and Average depth. You might already know the average depth. If not, this is the most difficult calculation, as you will need to measure depth in a few key places of your pond to figure out  the average. It is easiest if done with a boat and you can drop a line in a few spots and measure the distance to the bottom. 

Once the measurements are fairly accurate, you can use our calculator to determine both total gallons and acre feet of water.