How to Correct Nitrate Levels in a Fish Tank

New aquariums must complete the nitrogen cycle before the water is fish-safe and toxin-free. During the first three weeks of a new set-up, ammonia, nitrite and nitrate build up from excess waste and uneaten food until good bacteria colonizes the filter and substrate. This condition is known as new tank syndrome. Ammonia, nitrite and nitrate levels spike and kill your fish if left untreated. Monitor new tank water with a test kit and replace about 30 percent of the water every three or four days as a precaution to keep nitrate levels low.

Things You'll Need

  • Ammonia test kit
  • Nitrite test kit
  • Nitrate test kit
  • Beneficial bacteria solution
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Instructions

    • 1

      Test your tank water every day for ammonia to prevent a build-up of nitrate, using a kit. Check your reading against the manufacturer's color chart for an accurate result. If you are able to eliminate ammonia, or keep it in check, nitrate is unable to escalate. Nitrate appears in the third stage of the nitrogen cycle, after high readings of ammonia and nitrite. High ammonia levels are an indicator that nitrate levels are set to increase in a day or two, so replace a third of the water immediately and continue to check your water chemistry daily with a test kit.

    • 2

      Check your water for nitrite and nitrate with the appropriate water testing kits. Charts in your kit allow you to match your colored test result with an easy to read chart without any knowledge of chemistry. If your result is a dangerous color, and nitrate levels are already high, you must reduce them quickly, so change half of your aquarium water as an emergency treatment. Continue to check for all three toxins every two or three days.

    • 3

      Carry out a partial water change every three or four days, if necessary, to keep toxins at a manageable level. Change no more than a third of the water at a time, unless test results indicate dangerously high levels. The nitrogen cycle starts again from day one if you empty your aquarium and change all of the water. Never wash filter components and gravel in tap water because it destroys the beneficial bacteria, so clean tank items in a bucket of old aquarium water to sustain good bacteria breeding colonies.

    • 4

      Add a solution of commercial beneficial bacteria to kick-start your colony of good microbes. This action shortens the nitrogen cycle and keeps ammonia, nitrite and nitrate at safe levels until the water reaches a stability. Top-up your bacteria at every water change or with new fish to maintain a strong, healthy bacterial colony.