Aeration when used in terms of a pond is a process by which the water is oxygenated in order to keep it fresh and able to sustain fish life. If the water in a pond does not receive aeration, the water at the bottom lacks oxygen because it does not interact with the surface air where it could obtain more. This un-oxygenated water forms a layer which continues to grow in depth from the bottom of the pond upwards. As any fish that may be in the pond, have less and less oxygenated water to live off, they start to die whilst all the time, algae which thrive on un-oxygenated water increase. The pond will reach a stage where algae take it over, becoming unsightly and smelly. This is not a situation that most people would want and so they buy an aeration system and the system they buy will depend mainly on the depth of the pond to be aerated. For depths of up to 6 feet, a shallow aeration system can be used but if the pond is deeper than 6 feet, a diffused aeration system should be used. A fountain is a form of shallow aeration system as when it throws water into the air that water can be oxygenated. This is one of the reasons that many people have fountains in their ponds, because they aerate the pond as well as adding character to it. Another popular shallow pond aeration system is what is known as the propeller system. With the propeller system, propellers churn the water at the surface of the pond, not only allowing the nearby water to be oxygenated but also creating a circulation within the pond water so that all water in the pond can be oxygenated. What is considered the choice pond aeration system for deeper ponds is the diffused aeration system which is a system that uses a compressor, a diffuser and a length of hose to connect them. The compressor which of course needs a power source, is kept on dry land perhaps next to the pond and it is connected to the diffuser which is positioned at the bottom of the pond, by the air hose. The compressor pushes air through the hose to the diffuser, the diffuser releases that air into the water at the bottom of the pond where it continues to oxygenate the water all the way up to the surface, aerating the whole pond.
As all of these aeration systems need a power source of one kind or another and many ponds are located far from regular power sources, manufacturers sometimes include a power source in their aeration kits. One of these power sources is a windmill which, once set up can provide sufficient power for the aeration system it came with. Another power source used is solar and once again, once it is set up it will provide sufficient power to operate the aeration system it was supplied with. Some of solar kits can provide power for up to 3 days without additional sunlight.