The API® FRESHWATER MASTER TEST KIT measures the 4 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 FRESHWATER MASTER TEST KIT comes with 4 test tubes and a convenient holding tub for easy storage. The kit also includes a step-by-step instruction booklet with a color chart that provides information on how to correct unsafe water conditions. We recommend that you take a few minutes each week to monitor your aquarium conditions and create a better underwater world for your fish. Testing your aquarium water has never been so easy or accurate!