Why is aeration good for your pond and how does aeration work?
Oxygen or air affects the composition of water chemically and physically. Chemically, any dissolved minerals that are in the water become oxidized and are released out of the water source. Physically, any volatile organic matter is taken out of the water.
Depending to the level the water source is being cleaned - Aeration can be broken down into multiple components. Oxidization, Reduction, Precipitation and Filtration.
THE CHEMICAL PROCESS AERATION OXIDATION/REDUCTION
According to the Water Quality Association's Glossary of Terms, "oxidation is the loss of electrons from the reducing agent (which is said to have been 'oxidized' in the process). Since electrons carry negative charges, oxidation results in an increase of positive valence. Oxidation reduces the number of electrons orbiting an element causing the element to bond with oxygen, which has an attraction to those electrons. As this occurs you have oxidation and reduction.
Lets use the example of iron (Fe). It's a chemical that is most commonly found in water as its soluble state - ferrous bicarbonate, Fe (HCO3)2. Ferrous iron has a positive two valence. As ferrous iron is oxidized, the number of electrons is reduced and the iron develops a valence of positive three, ferric hydroxide, Fe(OH)3. To fully aerate iron, the amount of dissolved oxygen present must be at least 15% of the total amount of iron present. When dissolved oxygen is sufficiently present the iron and oxygen bond together. Soluble ferrous bicarbonate may be completely oxidized and changed to the insoluble ferric hydroxide precipitate, Fe (OH) 3, except when the water is acidic. The insoluble ferric hydroxide is commonly described as "red water". When iron is fully oxidized in alkaline water, iron readily precipitates.
One of the requirements for the successful precipitation of iron would be to provide it with sufficient contact time to oxygen so that the minerals can react. For iron removal, the more aeration, the more contact iron or any other mineral would have. Illustrating in a highly scientific way that, generally the best method of extracting unwanted matter from a pond is to have sufficient levels of oxygen. Whether in water tanks, lakes or ponds, aeration systems of any kind will assist in this process.
Precipitated iron or other matter can then be filtered once soluble in water. You would only go to these lengths if you planned on drinking the water or using it as a water source for human or perhaps even livestock consumption of some sort.