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The Best Way to Control High Nitrate Levels in Your Pond

Organic matter discharges nitrogen as it decomposes at a pond. The outcome may be ammonia, a chemical that has nitrogen as a key component, nitrites or nitrates. The organic matter may come from fish waste, dead insects or other creatures, or decaying plant material. The existence of nitrogen-based compounds is a part of the life cycle of a pond, but levels do need to be controlled to preserve overall pond health.


A good filtration system, correctly sized to your pond, will be the best defense against high nitrate levels. Beneficial bacteria that have nitrogen are a part of the filtration process, which is often executed with a bio-filter, or even a biological filter. Mature slopes eventually develop healthy bacterial colonies, but newer ponds may need a boost. Purchase some beneficial bacteria from a store that provides pond equipment. Cloudy water, a sharp scent, scum floating across the surface and algae blooms are indications that ammonia or nitrates may be building to dangerous levels. Examine the filter.

Water Chemistry

Purchase a test kit so you can keep tabs on essential water chemistry data for your pond. Routine tests — at least weekly — help alert you to changes from the pond’s chemistry. Because levels fluctuate throughout the day, make certain you take samples at precisely the exact same time each testing day. Evaluation kits to monitor pH, nitrogen and chlorine are an excellent beginning. Based on your findings, you will know whether you’ve reached a critical point in which you want to take actions to reduce or enhance water chemistry.

Minimize Organics

Clean out any dead leaves that fall into the pond and scoop out most of the muck that accumulates at the bottom of the pond. Skim the surface of the pond for organic matter such as grass clippings, plant material and dead insects or fish. The cleaner you can keep your pond, the less likely nitrates will build up to intolerable levels for plant and animal life.

Fish Attention

Fish food that settles to the bottom without being eaten is a key cause of high nitrates. When water temperatures are between 65 and 80 degrees Fahrenheit, feed fish twice a day, but just offer you sufficient food that they can eat in five minutes. When temperatures soared over 80 levels, stop feeding fish till water temperatures drop again. When water temperatures drop to between 55 and 65 degrees, fish metabolism slows, and you may feed them each day. Prevent overpopulating. The rule of thumb is no more than one inch of fish for every square foot of pond surface area, especially for newer slopes.


As plants create food, they absorb nitrates in the water and release oxygen back into the water. Add some live plants to your pond to help oxygenate the water. Plants help create a buffer that levels out potential spikes in ammonia and nitrates.

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