How to Lower the Nitrates in My Tank

Low levels of nitrates in an aquarium are not harmful to fish. However, excessive nitrates, 20 ppm or more, will cause the water to look dirty and stress your fish, leading to disease or death. To be able to lower the nitrate levels in your tank, you must understand the nitrogen cycle and what increases nitrates. In the nitrogen cycle of a fish tank, "good" bacteria break down the ammonia from fish waste and other debris into nitrites. Good bacteria then break down the nitrites into nitrates. High nitrate levels occur when there is too much ammonia in the tank -- a result of having too many fish, overfeeding, not changing the water often enough or inadequate filtration.

Things You'll Need

  • Water test kit
  • Siphon with vacuum
  • Bigger filter
  • Fish food
  • Live plants
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Instructions

    • 1

      Change 15 percent to 20 percent of the water in the aquarium daily. Before each water change, test the nitrate levels. If the nitrate levels have come down to a normal level, then you can stop the daily water changes. To prevent the nitrates from building up again, the authors of "Freshwater Aquariums for Dummies" recommend that you perform weekly water changes of about 20 percent.

    • 2

      Use a vacuum at the end of your siphon when making any water changes. Use it to siphon up loose debris from the surface of the gravel or sand in the tank.

    • 3

      Remove any floating dead plant leaves when cleaning the tank. You can do this by hand or by using a fish net.

    • 4

      Feed the fish twice a day and only as much food as they will eat in one minute. Your goal is to prevent any food from falling to the bottom of the tank and rotting.

    • 5

      Move some of the fish to another tank. Fewer fish in a tank will produce less ammonia to convert to nitrates.

    • 6

      Buy a new and larger filter for the fish tank. If you have a 20-gallon tank with a filter designed for a 10- to 20-gallon tank, move up a size to a 20- to 30-gallon filter.

    • 7

      Add live plants to your tank. Plants use nitrites and nitrates, removing these substances from the water.