The key to successful fish keeping is excellent water quality. The Aquarium Water Mini tests three water parameters: pH, Nitrite and Ammonia. Ammonia is excreted by fish as a waste product. It is extremely toxic to fish, and is broken down into less toxic nitrite by the beneficial bacteria in the filter of your aquarium.
Nitrite is produced by the beneficial bacteria in the pond and filters as they break down harmful ammonia excreted by fish. Although not as toxic as ammonia, nitrite is still very damaging to the health of the fish. Nitrite itself is broken down into nitrate which is significantly less harmful to fish.
pH is the measure of the acidity or alkalinity of the water in your aquarium. The pH scale runs from 0 to 14. Very acid water is pH 0 and very alkaline water is pH 14. Neutral water that is neither acid nor alkaline is pH 7.