How to Control Nitrites in a Fish Tank

In a small aquatic ecosystem such as a fish tank, waste builds up quickly. This waste releases toxins if it is not broken down. The microorganisms that break down toxic ammonia convert it to equally toxic nitrites; a second group of microbes then coverts nitrites into relatively harmless nitrates. If test kits show detectable levels of nitrites in your tank, you must take immediate action. In the short term, this means water changes. In the longer term, you need to establish a balanced ecosystem with enough microbes to handle the aquatic waste.

Things You'll Need

  • Nitrifying bacteria culture
  • Fish food
  • Aquatic snails
  • Ammonia, nitrite and nitrate test kits
  • Net
  • Second fish tank
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Instructions

    • 1

      Cycle a new tank before introducing any aquatic animals. A freshwater tank needs at least a week while marine aquariums take much longer. Set up a freshwater tank. Introduce plants and a nitrifying bacteria culture after one day along with a couple of flakes of fish food. Introduce aquatic snails after one week. Test the water periodically for ammonia and nitrites. Introduce fish one or two at a time once levels are no longer detectable.

    • 2

      Conduct regular water changes. Remove 10 to 25 percent of the water along with debris, using a gravel cleaner with a tube and a bucket. Put the end of the tube in the bucket, shake the gravel cleaner in the tank to get it started and focus on siphoning debris while you remove the water. Replace with fresh, dechlorinated water.

    • 3

      Test the tank water for nitrites, ammonia and nitrates weekly, following the manufacturer̵7;s instructions on the test kit. If ammonia or nitrite levels are apparent, conduct an immediate partial water change followed by others, if necessary. Stop feeding your fish for a couple of days. Feed the fish once tests show levels are back to near zero. Increase the frequency of regular water changes.

    • 4

      Ensure that your tank is not overstocked. Estimate the length of each fish and add the results. You should have no more than 1 inch of fish per gallon of water. It is best to under-stock. If your fish have grown or bred to exceed this level, transfer some to a second tank or sell them.

    • 5

      Avoid overfeeding your fish as leftover food decomposes, adding to toxins in the tank. Remove dead aquatic animals and dying plant leaves immediately.