What Causes Algae and Other Pond Problems?

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Algae, excessive aquatic plants, cloudy or murky water, odors and even lethargic fish are all problems that pond owners face, but what causes these problems?

Algae, excessive aquatic plants, cloudy or murky water, odors and even lethargic fish are all problems that pond owners face, but what causes these problems?

Simply stated, ponds with such problems have an ecosystem that is out of balance. This unequal balance is generally caused by too many available nutrients in the water and low oxygen content. Nutrients come from a variety of organic matter that is commonly found in ponds like dead leaves, grass clippings, fish food, fish and animal waste, dead algae and aquatic plants, fertilizer run-off and all sorts of other organic materials. The organic waste releases nutrients that are used by aquatic plants like algae, hydrilla, duckweed and other aquatic nuisance plants to grow and thrive. When excessive levels of nutrients are present these plants can grow fast and quickly take over a pond.

Normally a pond with a sufficient dissolved oxygen level will be able to break down and decompose the organic matter before it can be utilized by pond plants, however, ponds with lower oxygen levels will be slower to react and the organic matter will build. Eventually a situation will occur in which the break down of the waste will put a such a strain on the ponds oxygen level that the marine life, like fish, will become negatively impacted, due to the lack of dissolved oxygen available to them. In extreme cases there can be such low oxygen levels that fish kills occur.

In addition to the dead organic materials creating a strain on the oxygen levels, excessive outbreak of algae can have the same effect. Normally a small amount of algae is ok because pond plants like algae do release oxygen back into the water. It is when algae outbreaks get severe, that they too affect the pond’s oxygen level. During daylight hours, algae consume carbon dioxide from the water and release oxygen, but when night falls, this process is reversed and the algae begin utilizing the ponds oxygen to survive. So when there is a large algae population, oxygen levels can be significantly reduced in the over night hours leading to increased algae growth during the day.

Another byproduct of the cycle of poor organic material breakdown is the increased presence of odors. Material that is slow to breakdown can become anaerobic and emit pungent and noxious gases like ammonia and hydrogen sulfide. Again, under normal conditions where a pond has a healthy oxygen level, the matter is digested aerobically and no odor is produced, but when there is not enough oxygen to do the job, anaerobic microbes begin digesting the waste, creating the odors.

The introduction of aerobic bacteria (microorganisms) can be a welcome addition to most any pond environment. Aerobic bacteria aid in the ponds ability to efficiently remove organic matter and control the nutrient load. The bacteria also improve the pond’s dissolved oxygen level, making it more effective at organic matter breakdown and odor reduction. Aerobic bacteria are also compatible with most non-chemical pond treatments, which make it an easy addition to a pond maintenance program. To make an analogy, aerobic bacteria are to ponds, what fertilizers are to lawns. Fertilizers added to a lawn are intended to promote a healthy soil and enhance the color and thickness of the grass. A healthier grass and soil will resist disease and weeds. Aerobic bacteria do the same for ponds. They create an environment that is healthier and less conducive to normal pond problems.

Make no mistake, a harmonious balance between nutrients and oxygen is not the end-all be-all solution to all pond problems. Certainly there are diseases and other ailments that are started by other reasons, but having a healthy, stable pond environment goes a long way in preventing pond problems.

Contact: Casey Coke

Natural Environmental Systems, L.L.C.

5000 Quorum Dr. #300

Dallas, TX 75254



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