You need to consider several factors when choosing a pond aerator that will be adequate for the size and type of pond that you have. Consider size, the amount of fish or animals living in the pond, any other oxygenating factors like plants or streams, and your local climate. Aeration is equally important in winter as it is in hot weather. Heat reduces available oxygen for fish to breathe, while a frozen-over pond stagnates quickly without making a hole in the ice with an aerating kit.
Assess your pond size. If you don't have a volume estimate on your pond, get one by calculating your own pond volume. Measure the area with a measuring wheel or stick. Multiply approximate area by depth, and add 10 percent at the end to cover any rounding. You can also use the pond volume calculator in the Resources section. Aerators are usually recommended based on pond volume, so having this figure is important to choosing the right one.
Think about pond depth. A shallow aerator such as a fountain aerator is very decorative, but does not oxygenate the deeper waters of the pond. If your pond is shallow, however, it may be the perfect choice. For deeper ponds, an air diffuser aerator is the best choice, as it mixes air and water from the bottom of the pond up.
Check the setup around your pond. Is there electrical access nearby? If there is, an air compressor-type aerator is a good option for any size and depth of pond. A linear compressor or regenerative blower will aerate a shallow pond, while a higher-volume, high-pressure piston compressor will take care of a large, deep pond. In between, there are rotary vane, diaphragm and rocking piston compressors that may fit your pond perfectly.
Fit the aerator to the available resources. Without electricity nearby, an air diffuser is a good choice, as its tubes can run up to 2,000 feet away from the pond. But, keep in mind many air diffuser systems require that you weight the tubes, and keep filters and air stones clean regularly. All aerators do require regular maintenance, cleaning and a power supply.
If you are searching for an environmentally friendly or low-maintenance aerating option, and you don't have time or availability to maintain a complex aerator in your pond or do not want to add an electrical appliance to your energy use, look to greener options. Oxygenating plants added to your pond will add oxygen to your water, and native varieties are available at local nurseries. A small windmill placed on the shore of the pond also will aerate the surface by creating waves, and will save considerably on electric bills. Solar-powered pond aerators also are available.