Keep your fish healthy and thriving by testing your aquarium water's pH regularly with easy-to-use API pH TEST STRIPS for freshwater aquariums. Testing water parameters weekly helps prevent invisible water problems that can be harmful to fish. pH is the measure of acidity of water, on a scale ranging from 0 to 14. A pH of 0 is the most acidic, while a pH of 14 is the most alkaline. Different geographies have different tap water conditions with different pH levels, while fish require a specific pH level to thrive. A pH of 7.0 is ideal when keeping a community aquarium containing a variety of tropical fish. Goldfish and livebearers prefer a pH of 7.5. Many Amazonian fish, like angelfish and neon tetras, prefer a pH of 6.5 to 6.8. Mollies and swordtails thrive at pH 7.2 to 7.5. API pH TEST STRIPS for freshwater aquariums test a wide range of pH levels from 6.0 to 9.0. Just dip a strip directly into your aquarium.