Fish need properly balanced levels of ammonia, pH, high range pH, nitrite and nitrate. The API FRESHWATER MASTER TEST KIT measures these six parameters with scientific accuracy and provides professional results. It comes with four glass test tubes, a holding tray, test tube rack and computer calibrated, laminated colour card. Just fill the test tubes, add the test drops and compare results to the colour card. Then follow the recommendations on the card if action is required.