The pH of an aquarium is a very important, yet commonly overlooked aquarium water parameter. A correct, stable pH will help ensure a healthy aquarium environment. The pH of an aquarium can fluctuate due to biological or chemical activity within the aquarium. With Fritz pH Lower, the pH may be decreased to a desired level for aquarium inhabitants. Adjusting the pH to the proper level has an important influence on fish health and disease resistance. Directions: To decrease pH, add 5 ml (1 cap/1 tsp) per 20 gallons of water.