The Red Sea Fresh Lab kit tests measures aquarium water to detect if pH is too high, too low and how much ammonia and nitrite there is. This testing kits allows you to keep up with the health of your tank water to ensure pH levels are stable and maintained for the fish within the aquarium. Each tank has a biological filter that will convert ammonia to nitrite and then to nitrate, which is less harmful to the tank fish. This testing kit will test for ammonia and nitrite levels to determine if the biological filter is working properly. You can also use the chlorine kit to make sure you have a chlorine free aquarium.