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Aerate your pond for better water quality.

A pond or small lake located on your property is a very desirable assist for many people these days. Whether it is a small pool with a few ornamental fish in it or a large pond with varied uses, all ponds can benefit from aeration. With the varied uses of water (irrigation, fish growth, livestock, fire prevention, recreation, waterfowl, wildlife habitat and aesthetics), uses of water sometimes conflict. But no matter the use, the most important water quality parameter for lakes and ponds is dissolved oxygen. Oxygen is essential to all aerobic (air breathing) organisms. It can also be an effective lake management tool and necessary for keeping a body of water healthy.

Oxygen demand in water typically increases as the water temperature increases. The ability of water to hold oxygen decreases as the water temperature increases. For this reason there are certain cases where artificial aeration makes good sense.

Oxygen typically enters ponds and lakes at the surface via diffusion from the air or by wind action. In fact, in nature, oxygen is produced by wind, diffusion at the air/water interface, and photosynthesis from aquatic plants. For oxygen to move towards the bottom it must be absorbed or physically moved via wave action. Because the water carries so little oxygen organisms easily use it up before reaching the bottom. For this reason many lakes will have oxygen depletion at some point above the bottom. When a pond becomes thermally stratified, the warmer water on the surface does not enter the bottom depths because of the denser colder water on the bottom. Without mixing, oxygen does not enter the bottom depths. The problem is compounded in small deep ponds with trees that surround the water, which interfere with wind action. Without oxygen present:

* The organic muck layer on the bottom breaks down a lot slower.

* Oxygen-breathing, sediment-consuming, microorganisms are not present.

* Conditions are favorable for a buildup of gases harmful to fish.

* The effective living space for fish is reduced.

Benefits of aeration

* The ability to hold more fish and to prevent fish kills as the result of low or no oxygen levels.

* Potential control of filamentous (moss) or planktonic (green tinted water) algae.

* Elimination of the possibility of a fish kill due to a pond turnover.

* Potential control of mosquito larva. (During a certain stage in the growth of most mosquito larva they require a smooth water surface and suspend on the surface tension of the water breathing air through a siphon. If the surface tension is broke, larva can sometimes be effectively eliminated.)

* Odors such as hydrogen sulfide (rotten egg smell) can be effectively eliminated.

* Prevention of a winterkill due to ice covering of ponds.

* Wildlife refuge of open water in winter months.

Pond shape can affect the type and amount of aeration required. Long, narrow ponds can be difficult to aerate with just one unit because :he area of influence is limited. In this case two or more units may be spaced equally apart to adequately aerate and mix the water.

Types of pond aeration

Diffused air: Diffused aeration systems are typically some type of shore-mounted compressor with an airline and a bottom-mounted diffuser used to break up the air into small bubbles.

Advantages of diffused aeration include:

* They are fairly efficient in deeper ponds because they bring bottom water up to the surface.

* There is no electricity in the water.

* There is a gentle rolling action at the surface.

Disadvantages include:

* Efficiency drops off in shallower ponds (under eight feet).

* Compressors require cleaning or air filters, bearings and vanes need periodic replacement.

* Some diffusers can clog over time, which requires them to be lifted out of ponds and cleaned.

Variations to an electric 115 volt compressor source include windmill aerators and solar units. Windmill aeration basically has some type of diaphragm compressor that functions whenever the wind blows. So the obvious disadvantage to this approach is that it does not work when you need it the most--the lazy-hazy days of August when oxygen demand is the greatest. Solar units basically employ a solar panel that collects the sun's energy and converts it into a power source which is then used by a compressor to pump air into water. The disadvantage to this approach is that these systems can be costly for the small amount of air produced, but they might be your only choice in some cases where power is a great distance from the water source.

Fountains: Fountains can be defined as water pumping devices that uses electrical power to create an aesthetically pleasing display. They work well in small ponds that are relatively shallow. As water is pushed higher and higher into the air the effiency of these units decline. In theory you probably only need to splash the water a couple of feet into the air for the water to obtain its saturation level of oxygen. Pushing it higher compromises flow rate in favor of height, which then affects the device's oxygen transfer rate. Fountains typically only move water from depths no greater than 10 feet, because their intakes are close to the surface. Hybrid aerating fountains have typically been a decent choice for aerating ponds. These devises give you the best of both worlds in that they give you an aesthetically pleasing display, as well as decent transfer of oxygen into the water. A "V" pattern fountain would be a good example of a fountain that aerates as well as gives you something pretty to look at. Many people also like the display because it can attract attention to your location and add beauty at night with lights.

Horizontal water movers: This type of device uses a pump that causes a horizontal flow of water to create water movement. They are an excellent choice for long canals in which there is no demand for a pleasing display at the surface. The water currents created by these devices can interfere with the ability of certain algae to get started and they can also keep areas clean of debris.

Surface agitators: These units will employ a float, motor, and prop to splash water at the surface to create oxygen transfer into the water. The display produced is basically a frothing action at the surface.

When purchasing aeration the following criteria should be used:

* Minimal maintenance

* All components should be safety tested as a package or complete units.

* Simple

* Lead-time from the supplier

* Aesthetically pleasing display

* Cost which includes initial, electrical and maintenance.

Aeration should not be viewed as a lake management panacea. Low dissolved oxygen levels and stratification can be controlled by:

* Wise use of certain aquatic herbicides and dyes

* Introduction of organic consuming beneficial bacteria.

* Creating buffer zones of plants that act like filters around the water's edge to curb nutrient additions during rainfall events.

* If feeding fish, do not feed them any more feed than they will consume within five minutes.

* Create a berm and swale so that runoff water is filtered prior to entering the water.

* Fertilize wisely and never before predicted rains.

Usually a combination approach of the above including aeration is the wisest approach.

The benefits of a properly applied aeration system have long been demonstrated to be effective tools in water quality management. The relatively low cost of aeration is well rewarded with enhanced water quality and can be a very effective lake management tool. It can also bring beauty to your pond and create a tranquil setting for reflection.

For more information on pond aerators, contact Bob at: Bob.r@kascomarine. corn (see ad on page 111)

BOB ROBINSON

FISHERIES BIOLOGIST

KASCO MARINE
COPYRIGHT 2007 Countryside Publications Ltd.
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Title Annotation:Homestead water
Author:Robinson, Bob
Publication:Countryside & Small Stock Journal
Date:Jul 1, 2007
Words:1267
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