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. Water with a pH of 7.0 is considered "neutral". Different geographies have different tap water conditions with different pH levels, while fish require a specific pH level to thrive. API Proper pH 7.0 Freshwater Aquarium pH Stabilizer automatically sets and stabilizes the pH level in freshwater aquariums to 7.0 which is perfect for a mixed variety of tropical freshwater fish. API PROPER pH 7.0 Freshwater Aquarium pH Stabilizer also removes toxic compounds from tap water such as chlorine, neutralizes chloramines, detoxifies heavy metals, and adds electrolytes, making tap water safe for fish. Use this aquarium treatment when setting up a new aquarium, adjusting pH, or changing water. pH in an aquarium can fluctuate due to fish waste, uneaten food and addition of tap water. It is recommended to test water for pH weekly. With API aquarium products, its easy to keep a beautiful saltwater, freshwater or reef aquarium. For almost 60 years API has developed premium solutions with proven and effective results for your family and ours. API offers a range of testing kits, water conditioners, and nutritionally superior food, because were dedicated to making a better underwater world. They work to provide a safe, hospitable environment for fish such as tropical community fish, cichlids, goldfish and more. At API, we understand the rewards and relaxation of fishkeeping because we have a passion for fish too.