Subsurface pond and lake aeration…. the right choice for the serious pond owner

Lake and ponds are living aquatic ecological systems, which have fish, vegetation and various types of organisms, both vertebrates and invertebrates, all of which require oxygen to live and thrive. This living aquatic environment places a continual oxygen demand on the aquatic environment. Most pond owners don’t realize that it’s not a question of “if”, but a matter of “when” they could face the consequences of a fish kill due to oxygen depletion. This problem is a regular occurrence among pond owners. Oxygen depletions can be prevented by properly aerating a lake of pond. There are several different types of aeration available to the pond owner, some more effective than others. To be able to understand the best method of aeration, one must first understand how aeration works and why it is necessary for the success of a pond or lake.

How Subsurface Aeration Works

Aeration of water is achieved by exposure of water to air, which contains oxygen. In nature, wind activity provides this in large bodies of water by creating waves, which both moves the water by creating currents and also oxygenates it by exposure to the air. Subsurface aeration has the unique ability to create what is known as an airlift current from the bottom to the top of the pond, while at the same time introducing oxygen to the water through millions of tiny air bubbles. The air bubbles rising from the bottom to the surface of the pond originate from a configuration of self-cleaning flexible membrane diffusers. This aerates the pond through the most economical and efficient method: de-stratification. The assembly used was developed through extensive testing of underwater current flow analyses, and can lift the maximum amount of water from the bottom to the surface using the minimum of horsepower energy.

Advantages and Benefits of Subsurface Aeration

Sub-surface aeration provides many benefits and advantages over most all methods of surface aeration.

• Superior Oxygenation Efficiency – The purpose of any pond aeration system is to introduce oxygen into the water column. Oxygen efficiency is the measure of the amount of oxygen (in pounds of oxygen per acre) created by one horsepower of energy. The Sub-Surface aeration systems provide the best oxygen efficiency of any aeration system. This means they are the best investment for the dollar. This high oxygen efficiency is achieved due to the fact that so much surface area of air (from the literal millions of bubbles that create huge amounts of surface area) is coming in direct contact with the water, which translates into “water touching bubbles” in layman’s terms. Because these systems require very little horsepower to operate (IE: low energy costs), the net cost to produce the oxygen is greatly reduced, thus substantially increasing the oxygen efficiency. By starting the bubbles at the bottom of the pond and allowing them to rise up the entire column of water, the water in the pond is exposed to a tremendously larger amount of oxygen than a traditional surface aerator could ever hope to create. In addition to this, the use of fine bubbles is far more efficient than that of coarser bubbles. This is due to the higher amount of surface area of many smaller vs. one large air bubble.

• Oxidation of Waste – Most pond owners are very serious when it comes to their lake or pond. In most cases, their expectations are high and in an effort to achieve their goals and objectives and enhance or improve the productivity of their ponds, they employ aggressive management practices such as fertilizing, vegetation control and management, and regularly feeding their fish. The byproduct of these activities is waste! Waste products are generated from various sources such as fish wastes, unutilized fish feed, dying or decomposing vegetation and leaves from surrounding trees, organic and inorganic sediment deposits from nearby runoff and nutrient build ups from all of the aforementioned. These waste products accumulate at the bottom of the pond and contribute to the buildup of silt – the thick black mud like substance that builds up at the bottom of the pond and produces very foul odors. These waste products, mostly organic in nature, need to be biologically decomposed. The decomposition process is called oxidation and in order that the organic wastes be most effectively broken down and ultimately decomposed, large amounts of oxygen are required. Unfortunately in most all ponds, there is far too little if any oxygen at the bottom of the pond, where the matter that needs to decompose is located. The result of this is that a huge BOD (Biological Oxygen Demand) is created and is constantly present at the bottom of the pond, just waiting to consume all the oxygen in your pond in the event that the oxygen becomes available to be utilized by the BOD. Pond Turnovers or Pond Inversions, a very common occurrence in small ponds, especially in the summer time, usually resulting in total fish kills, occur when oxygenated water comes in contact with the huge reserve of un-decomposed material on the bottom of the pond. The result is that any resident oxygen in the water is sucked up like a vacuum by the matter that needs to be decomposed. This spells disaster for any fish in the pond, since all the water is literally “instantly robbed” of oxygen. The most common time when this occurs is after a cold, hard rain in the heat of summer.  The colder rain water, which is denser, pushes its way down to the bottom of the pond, mixing up the un-decomposed material into the water column. When subsurface aeration is employed, this does not occur because the pond does not get stratified in this state, and the silt is slowly decomposed at the bottom of the pond due to the introduction of oxygen on a consistent 24 x 7 basis by the airlift diffuser.  As a result, silt buildup in the pond bottom is minimized. This protects the pond owner from experiencing the dreaded “fish kill” and loosing the entire investment in time, effort and money they have in their fish inventory. In addition, the pond owner does not have to periodically drain, and hope for months of dry weather, and then mechanically remove the silt from the pond. This process can take from three (3) to twelve (12) months to complete and is very costly.

• Water Circulation and De-Stratification – The massive airlift current generated by the airlift assembly on the bottom of the pond moves a large amount of water from the bottom to the top of the pond and then back down again. This eliminates what are known as thermoclines in the pond. Thermoclines are strata of water that vary substantially in temperature. The lower layers of water in the pond are colder water, and it is the area where there is naturally less oxygen than on the surface where there is more oxygen and the water is more readily exposed to oxygen transfers. The deeper the water, the more apt the pond is to develop a thermocline. Ponds less than 4’ in depth rarely develop a thermocline. When a thermo cline develops in a lake or pond, it greatly slows down and almost entirely inhibits the transfer and exchange of various gases between layers. That means that the escape of the bad gases from the bottom to the top is slowed and the penetration of much needed oxygen to the lower layer is greatly inhibited. This ultimately results in the ultimate disaster know as a pond turnover - the pond owners “dreaded nightmare”. By constantly, and gently mixing the water in your pond, subsurface aeration systems eliminate this phenomenon. Surface aerators cannot accomplish this unless they are drawing from the bottom of the pond. Even then, the surface aerators do not generate the airlift current of water, nor do they provide the aeration efficiency that is produced from the subsurface systems.

• Water Purification – In most non-aerated ponds, unusually high amounts of harmful and sometimes deadly bacteria develop from the “literal cesspool” of wastes. These bacteria can be found in the water column, but the majority find themselves embedded and building up on the accumulated wastes in the bottom of the pond. If the wastes and bacteria continue to increase, the pond ultimately can become polluted and stagnant in nature, thus totally unproductive. The boiling current of the airlift diffuser aids in countering this by pulling water from the bottom of the pond and pushing it to the top, where it is exposed to the ultraviolet rays of the sun. The sun’s rays destroy harmful bacteria and thus aids in the rectification of the water quality and ecological environment of the pond.

• Enhanced Water Quality– Fish do not grow well in ponds with poor water quality, and especially when oxygen levels are low or constantly incurring drastic oxygen fluctuations. In addition, humans are taking a risk by swimming in ponds that have poor water quality conditions, as harmful bacteria can be dangerous to ones health. By increasing and supplying the appropriate amount of oxygen and distributing it throughout the pond, and thus oxidizing the waste, you are in essence increasing the beneficial aerobic bacteria (which can now stay alive because they have the ability to live on or near the bottom because of the presence of oxygen). These bacteria consume the waste products on or near the bottom of the pond, thus decreasing the presence of pond waste, and enhancing and improving water quality. This creates a much improved and healthier aquatic environment for your fish, your plants or for water sports entertainment.

• Aids in Algae Reduction – Most pond owners are plagued by algae. It is the single – most unwanted type of vegetation in small ponds. The most common form of algae that is problematic for pond owners is called filamentous algae – the scummy and slimy stuff growing on the surface or around the perimeters of most ponds. Algae are single celled plants, which thrive in ponds where there is an abundance of unutilized nutrients, and/or sunlight penetration reaches over 1 foot in depth. In addition, algae thrive best when water quality conditions are the worst. At least 90% of small ponds meet these criteria. When aeration systems are employed, available nutrients are highly utilized and thus reduced by the abundance of aerobic bacteria, thus starving the algae of food and tremendously reducing the amounts of algae. In many cases, the savings in chemical costs to control algae offsets the cost of a subsurface aeration system.

For more information, please contact Texas Lake Management at 830-626-6206.