by Aaron Hunt

Created on: June 02, 2010

High nitrate levels in the aquarium can affect the growth and overall health of fishes.  It also encourages algae growth, can affect the behavior of fish, and prevent them from showing the best color.  To understand how to reduce nitrates, it’s important to understand what they are and their potential sources. 

Nitrates in the aquarium are created when beneficial bacteria break down fish wastes.  The waste start as ammonia, and bacteria in the tank convert the ammonia into nitrates as part of the nitrogen cycle.  Nitrates are much less dangerous to fishes than ammonia or nitrites-the middle part of the cycle.   The term “cycling” a new aquarium refers to growing the bacteria that convert ammonia to nitrites and then into nitrates.  Ammonia and nitrites can cause stress at less than 1 part per million; nitrates are safe up to a level of 80-100 parts per million, although lower is better. 

Nitrate levels can also be affected by other factors, such as over feeding, decaying plant matter, or having an overcrowded aquarium.  All of these sources can be overcome with one technique for lowering nitrates: the partial water change.  It’s easy, inexpensive, and effective.  A partial water change encourages growth and vitality in fishes.  It is often used by advanced aquarists to trigger spawning.  Other than choosing healthy, compatible tank mates for the aquarium, it is the single most important step in keeping healthy, long-lived fish. 

The water change is simple to perform.  Required equipment is a bucket that has never been used for detergents or chemicals, a combination siphon and gravel vacuum, and a source of dechlorinated water.  Using the gravel vacuum, siphon between ten and forty percent of the water out of the tank and into the bucket, siphoning the gravel at the same time.  Siphoning through the gravel pulls detritus and debris out of the gravel than contribute to high nitrates and it also prevents fish from getting siphoned out of the tank.  Continue to siphon the gravel using a pogo-like motion – up and down – plunging into each new section of gravel until the desired amount of water is removed. 

Refill the aquarium with dechlorinated water that matches the temperatures of the aquarium.  Most communities have tap water that is very good for aquaria.  However, some locations may have nitrates in the tap water. 

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