Types of Aeration

Fine and Coarse Diffusers

Although coarse bubble aeration appears to be effective, this is only visual. It is estimated that the aeration efficiency of fine bubbles is 6.6 times greater than that of coarse bubble aeration. Therefore, fine bubble aeration creates an efficient vertical circulation. This continual upward motion of the fine bubbles de-stratifies the water body. Fine bubble diffused aeration, therefore, effectively mixes water and reduces potential anaerobic sediment. This ultimately greatly improves water quality. See the bubble for more information

Injectors

Injectors mix air and water together by providing a jet of water containing air bubbles. In turn, this jet of water creates good horizontal movement of the water. This form of aeration is often very efficient, and as such the processes can be used for injecting oxygen into the water. However, when the process is used with air, supersaturation with nitrogen gas can occur. This leads to possible gas bubble trauma or sublethal toxicological problems. The systems generally fail to vertically mix the water column and to bring oxygen-enriched water to the sediment in the pond. Under these conditions it is likely that the sediment will become anaerobic.

About Mechanical Agitation and Fountains

There are a wide variety of surface agitators such as paddle wheels and pumps. Each of these systems expends a great deal of kinetic energy in throwing large quantities of water into the air. This means that energy is not directly used to aerate or mix the water in the fish culture system.
Surface agitators often look very impressive but their actual influence over oxygen levels in the aquaculture system is localized to the area surrounding the equipment. This factor becomes very apparent in ponds with a water depth of more than 1 metre. Very low oxygen levels may be recorded if taken at depth or in the sediment. The low dissolved oxygen levels may lead to anaerobic sediment conditions and deterioration in water quality.