Quickly measure and modify the six aquarium levels that are most important to the health of your freshwater fish with the API Freshwater Aquarium Master Test Kit. To stay healthy and thrive, fish need properly balanced levels of ammonia, pH, high range pH, nitrite and nitrate. These levels can change rapidly and create harmful conditions when fish waste, uneaten food or other organic matter accumulate, or when untreated water is added. The API Freshwater Aquarium Master Test Kit measures these six parameters with scientific accuracy and provides professional results. It comes with four test tubes, a holding tray, test tube rack and computer calibrated, laminated color card. Just fill the test tubes, add the test drops and compare results to the color card. Then follow the recommendations on the card if action is required.