Diffused aeration systems utilize the power of air to de-stratify the water column and infuse oxygen into the pond. Typical set up involves an air compressor that pushes air through tubing down to diffuser(s) located and the bottom of the pond. When the air reaches the diffuser, the diffuser breaks it up into tiny bubbles that are released into the pond. The bubbling action of the air rising to the surface causes the water to de-stratify, meaning the poor, oxygen deprived water at the bottom of the lake is mixed with the oxygen rich water above, causing noxious and harmful gases to be released into the atmosphere. At the surface, where the bubbles break, additional oxygen transfer is made adding to the overall oxygen content of the water.
Diffused aeration is typically used in larger/ deeper ponds and lakes of more than 8 ft deep. Diffused aeration is more energy efficient where large ponds are concerned while also offering the advantage of keeping electrical wires out of the water. They also cause very little surface agitation for people who like a smooth look to their pond or lake
Surface aerators, as their name suggests, are located at the ponds surface. These units utilize a pump mounted beneath a float that pumps water from the pond into the air or right at the surface. Unlike diffused aerators, surface aerators are best used in shallow ponds and lakes. Oxygenation using floating aerators occurs when the water that is splashed into the air makes contact with the ponds surface when it comes back down. This interaction allows for the venting of gasses and the transfer of oxygen, however because all of the pumping of water and oxygen transfer occurs at the surface, very little benefit is gained at the lower depths.
Surface aerators can also serve a dual purpose. Aside form the primary function of oxygenating water, surface aerators can add aesthetic appeal as they are available with different spray patterns. However, if aeration is to be the primary function of the unit, it is important to select an aerator that creates a fine mist and a wider display. These types of units allow for greater venting and oxygen transfer as they create more turbulence at the pond's surface.
In summary, when attempting to select a pond aerator, be sure to take pond depth and size into consideration to help you determine if a diffuser aerator or surface aerator will be the best choice.