Nitrite is a toxic nitrogen compound, which is formed when the bacterial balance is disturbed or when setting up a new aquarium. The test shows the exact nitrite content of the water Laboratory comparator system to compensate the inherent water colour: fill glass vials with sample water, add reagents to one vial, place vials in holder, read values off colour chart Use: when setting up a new freshwater aquarium: daily for 3 weeks. For initial setup with marine water: once a week. For use with fish diseases or fish deaths You will find detailed information and troubleshooting tips about water analysis on the JBL website in Essentials/Aquarium or Pond Package contents: 1 nitrite test for approx. 50 measurements, incl. 2 reagents, 2 glass vials with screw caps, syringe, comparator block and colour scale. Reagent refill separately available