he 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 Kit for freshwater aquariums test a wide range of pH levels from 6.0 to 9.0. Just dip a strip directly into your aquarium, and use the color-coded chart to determine if your water is safe or if adjustments are needed. Then follow the recommendations to treat the water â it's that simple!