The API freshwater master test kit measures the four most important levels in freshwater aquariums quickly and accurately, including pH, high range pH, ammonia, nitrite and nitrate. With scientific accuracy for professional results, the reusable freshwater master test kit comes with four glass test tubes with snap-tight caps and a convenient holding tub for easy storage. Also includes a step-by-step instruction booklet with a color chart that provides information on how to correct unsafe water conditions.