Nitrate (NO3)

Nitrate is a by-product of the Nitrogen Cycle, it is also used in explosives. The bacteria, Nitrobacter, converts the toxic Nitrite into Nitrate. Nitrate slowly builds up over time. The speed at which they build up depends on a few factors like: pond size, fish stocking levels, feeding levels, temperature and Nitrate levels in the ground water. Nitrate will also come from decaying leaves and other plant material in the pond. Koi can live in Nitrate levels up to 100 ppm, but a level around 20 ppm is much, much better.


A high level of Nitrate will stress a Koi and will be detrimental to it's immune system. A high level of Nitrate will also affect a Koi's reproductive system and will stunt a Koi's growth. Elevated levels of Nitrate will also cause algae blooms, which will make a pond look like a bowl of split pea soup. Nitrate levels can be reduced by performing regular water changes, by adding vegetation to a pond, and by reducing the amount of food that the Koi receive. A good rule of thumb is to change at least 10% of the pond water a week. Change more water if the pond is heavily stocked or if the Koi are receiving a lot of food.


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