The pH of water measures the acidity or base of your water. pH is very important in keeping healthy fish because high or low pH levels can stress fish and puts their overall health in jeopardy. The pH scale ranges from 0 to 14 with 0 being the absolute most acidic water can be and 14 being the absolute most basic your water can be. pH balance, or a neutral pH value, is 7. Most freshwater fish thrive when you have a pH level between 6.6 and 7.8. If, after conducting a pH test, you find the pH level to be unacceptable, you can raise or lower your pH levels by purchasing chemical products from your local pet store such as Aquarium Pharmaceuticals pH Up or pH Down. Maintaining a consistent pH level that is suitable to your fishes needs is the first step towards consistently high water quality.