API High Range pH Test Kit Use this kit to measure pH to maintain a healthy African Cichlid, Marine or Goldfish Aquarium. pH is the measure of acidity of water. A pH reading of 7.0 is neutral. A pH higher than 7.0 is alkaline, and a pH lower than 7.0 is acidic. Maintaining the aquarium at the proper pH ensures optimal water quality. The pH should be tested weekly, since natural materials in the aquarium (such as fish waste and uneaten food) can cause pH shifts. *Reads pH from 7.4 to 8.8 *For freshwater and Salt water use