API 5 in 1 Aquarium Test Strips are a product for testing the water quality of both freshwater and saltwater aquariums. With 25 tests per package, these strips can measure pH, nitrite, nitrate, carbonate hardness, and general hardness levels. They are suitable for use in cleaning and maintaining fish tanks and are a must-have for pet owners who want to ensure the health and well-being of their aquatic pets.