JBL ProAquaTest No2 NitriteQuick test to determine the nitrite content in freshwater marine aquariums & ponds 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: