In a properly cycled tank, nitrites are eventually converted into harmless nitrogen gas. If your nitrogen cycle is breaking down somewhere, you could start accumulating nitrites, which are highly toxic to fishes and invertebrates. Nitrite test kits often suffer from inaccuracy due to interference by amines (amino acids) and Salifert's Nitrite Test Kit does not, offering full, precise results in 1 minute and bold colors for easy comparison.
The temperature of your aquarium water has to be above 64 degrees F. otherwise the complete color will not develop in 60 seconds. If the temperature is too low, keep the water in the test tube at room temperature for 10 minutes before testing.
With the syringe add 1 ml of water to the test vial.
Add to this 1 level spoon of the NO2 powder. Swirl the contents of the vial gently for 20 seconds. Allow to stand for 3 minutes.
Place the open test vial on top of the color chart on the part of the chart that is white and compare the colors looking from the top. Read the corresponding nitrite content. An intermediate color corresponds to an intermediate nitrite content.
Important: If the carbonate hardness is above 10 dKH (which corresponds to an alkalinity of 3.5 meq/L) addition of 2 level spoons in step 2 is required.
The nitrite values are in ppm nitrite. If you prefer a reading in ppm nitrite-nitrogen then multiply the reading by 0.3 or use the table given with the directions.
After your tank or pond has cycled you will need a much higher sensitivity. This is easily accomplished by looking through the side when comparing colors. Hold the test vial with its side against a white piece of the color chart.
These readings need to be divided by 10. In this way you will be able to detect 0.01 ppm at nitrite or 0.003 ppm as nitrite-nitrogen easily.