How to Test for Nitrates

In aquariums, decaying food, plant debris and fish waste break down into ammonia, which is toxic. Beneficial bacteria that live in the water naturally convert the ammonia into a slightly less toxic substance called nitrites, which are then converted by bacteria into nitrates. Nitrates are much less toxic to life. This is called the nitrogen cycle, and it is vital for the health of an aquarium. The nitrates need to be regularly removed from the aquarium by exchanging the old water for fresh. Basic liquid nitrate test kits are a quick and easy way to measure the buildup.

Things You'll Need

  • Nitrate test kit
  • Water sample
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Instructions

    • 1

      Purchase a basic nitrate test kit from a pet store that sells fish supplies. The kit will include 1 glass test tube with a plastic cap, 2 bottles of nitrate testing solution with eyedropper caps and 2 plastic cards with color-comparison charts.

    • 2

      Rinse the test tube with tap water to get rid of debris. Don't use soap.

    • 3

      Fill the test tube to the top with water from the aquarium you want to test and dump it out to get rid of any tap-water contaminants.

    • 4

      Fill the test tube with a sample of aquarium water up to the line printed on the side. Most kits use about 5 milliliters.

    • 5

      Add 10 drops of test solution marked "#1" to the test tube by holding the bottle upside down vertically over the top of the test tube and gently squeezing. Count each drop as it falls into the tube. Some test kits may indicate more or fewer drops are needed depending on the brand.

    • 6

      Fit the cap on the test tube. Turn it upside down and back a few times to mix it up. Do not cap the tube with your thumb; you could contaminate the test.

    • 7

      Shake the test solution bottle marked "#2" vigorously for 30 to 60 seconds to mix it up.

    • 8

      Add 10 drops of the second solution to the test tube. The number of drops may vary by brand.

    • 9

      Cap the test tube and shake it for 60 seconds or more to mix the solutions thoroughly. Set it down and wait 5 minutes for the color to change. The time may vary slightly depending on brand.

    • 10

      Hold the test tube against the white part of the color chart on the appropriate card. One card is for freshwater and the other for saltwater. Match the color of the liquid in the tube to the closest match on the card. This will give you your total nitrates in parts per million (ppm) and milligrams per liter (mg/L).