Adding air to a pond has a hugely positive impact on the ecosystem. It circulates water, disrupts mosquito breeding, adds oxygen for fish and other critters, and it helps prevent algae and other weeds. Aeration is by far the best value for money in terms of good pond health.
Aeration can come in many forms: aerators, fountains, windmills, circulators, and electric compressors. By far, the most common are pond aerators and fountains.
Pond aerators and fountains provide lovely visuals; this is true for fountains, especially, and aerators to a far lesser degree. Both mechanisms hang under a donut-shaped float and use a motor-driven propeller to shoot water up into the air. The main difference between a fountain and an aerator is that a fountain forces the water through a nozzle at high pressure, creating a specific display, whereas the aerator has no nozzle.
Using pond aerators and fountains do not provide the same oxygenation at the bottom of the pond as an air compressor, and usually isn’t as successful at fighting algae and weed growth. Pond aerators and fountains will circulate the top layers of water, keeping the pond surface free of scum and tree pollen. The benefit of this function is that they do not disturb the lower levels of pond or lake water, ensuring a better environment for trout and other cold-loving fish. Another advantage with pond aerators and fountains is that they do an excellent job of aerating shallow water bodies where you may otherwise need a large number of diffusers or an air compressor.