Why Test? The pH value of water is a measure of the degree of acidity or alkalinity, with values ranging from 1 (acidic) through 7 (neutral) to 14 (alkaline). It is important to monitor the pH of your aquarium water because all forms of life can show adverse reactions if kept outside their preferred pH range, or if subject to sudden changes in the pH value. This kit is professionally developed to accurately determine the pH level in your aquarium water for the safety of your fish. For freshwater aquariums only. Shipping weight: 1/4 lb.