API GH & KH Test KitWhen keeping freshwater fish and plants, the general hardness (GH) and carbonate hardness (KH) of aquarium water should match their natural habitat. The API GH & KH Test Kit helps you duplicate the natural habitat of your fish to prevent stress, keeping them healthy! The kit includes 2 bottles of liquid reagent, 2 glass test tubes with snap tight caps, and step by step instructions. We recommend that you take a few minutes each week to monitor your