The general hardness (GH) and carbonate hardness (KH) of aquarium water should match that of the natural habitat of the fish. Otherwise, fish will be stressed and prone to disease. Since adding tap water increases the hardnessof aquarium water, frequent GH and KH testing is essential. This test kit measures the general hardness (GH), the measure of calcium and magnesium in water, and carbonate hardness (KH), the measure of carbonate and bicarbonate concentrates. Proper GH and KH levels are an important part of water quality and are necessary for the health of fish and the development and growth of aquarium plants. Maintaining good water quality is the key to successful fishkeeping. This kit helps you create the perfect water conditions with stable pH, for healthy and colorful fish and plants. The kit contains: two dropper bottles for accurate dispensing of test solutions, easy-to-read instructions, and non-staining glass test tube with snap-tight cap.