In the past decade or two, ponds have become very popular with an increasingly wide variety of people, and with that, so has the demand for new, environmentally friendly techniques for the maintenance and rejuvenation of these ponds. Considering the costs of constructing a pond, it makes good economic sense to prolong the life of your pond. One of the simplest and most economical ways of doing this is to use aeration.

Aeration is the process of adding oxygen to water. Maintaining healthy levels of dissolved oxygen (DO), one of the most, if not the most important water quality parameter, in your pond aids in the breakdown of decaying vegetation and other sources of nutrients that enter your pond. This breakdown of bottom silt is carried out by microorganisms at the water/soil interface and continues to proceed a few centimeters deep in the soil. This decomposition can be carried out in two ways, aerobically and/or anaerobically. Aerobic decomposition requires a continuous supply of oxygen and proceeds more rapidly as dissolved oxygen concentrations near saturation levels. The rate of degradation of organic matter in anaerobic conditions is not as rapid as under aerobic conditions, and the end products are organic compounds, such as alcohols and foul-smelling organic acids (the sulfury pond muck smell!). In other words, the decomposition is slower and less complete in anaerobic environments than in aerobic habitats where the primary end product of decomposition is carbon dioxide. So what we can learn from this is, the more decomposition we can facilitate, through the addition of oxygen with aeration, the less nutrients there will be available for algae blooms and excess aquatic plant growth.

          Nature supplies, at times, sufficient amounts of aeration and dissolved oxygen through wind, rain, splashing of water from an incoming stream or waterfall, and by photosynthesis carried out by aquatic vegetation within the pond. However, as nutrients are added to the pond or body of water from sources such as runoff, dust from construction sites, grass clippings, and leaves from nearby trees, the demand for oxygen increases. When you add that to the fact that warm summer water holds less dissolved oxygen, and the demand for it increases during this time, you have a formula for fish kills, algae blooms, foul odors, and the build up of stagnant vegetation.

Aeration can help Mother Nature keep up with the demand for dissolved oxygen and prolong the life of your pond. Aeration increases the level of dissolved oxygen so normal biological processes in a pond system can become balanced. It also helps to move water in low circulation areas (which otherwise can build up undesirable levels of algae), and facilitates mixing throughout the pond if chemical treatment is necessary. In short, aeration provides a way to help clean up stagnant ponds and improve water quality for irrigation purposes.

Affects on Dissolved Oxygen

Barometric pressure, altitude, salinity, water purity, and biological oxygen demand all affect the amount of naturally occurring dissolved oxygen levels in water. The amount of additional oxygen water can hold through the aeration process is a function of temperature, altitude, and salinity. Colder water holds more oxygen than warm, water in higher elevations or with higher salinity levels has a decreased saturation level of oxygen. Once you have reached the saturation level, oxygen cannot be added without the help of photosynthetic activity or the introduction of pure oxygen.

In ponds, the introduction of oxygen via some type of aeration device can:

• Allow for greater densities of fish
• Eliminate the potential for Spring and Fall turnover
• Prevent wither kills caused by low oxygen levels
• Improve overall water quality
• Speed up the rate of organic decomposition
• Reduce the amount of phosphorus, which would otherwise be available for plant growth
• Thermally and chemically destratify the water
• Cause circulation currents that might create favorable conditions for more desirable algae to out compete blue green algae
• Decrease the severity of algae blooms and algae die-offs
• Shift the level of carbon dioxide by venting it into the air, which could limit the amount available for plants