Keep your fish healthy & thriving by testing your aquarium water's gh levels regularly with this easy-to-use api gh & kh test kit for freshwater aquariums. Testing water parameters weekly helps prevent invisible water problems that can be harmful to fish. Water hardness is a measure of the dissolved mineral content of water. There are two types: the general hardness (gh) & carbonate hardness (kh). When keeping freshwater fish & plants, the gh & the kh of aquarium water should match their natural habitat. The api gh & kh test kit helps aquarists duplicate the natural habitat of their fish, as well as detect low kh levels, which can lead to rapid & wide ph shifts, stressing fish. Api gh & kh test kit contains kh test bottle, gh test bottle, instructions with color card, & two capped glass test tubes. With api aquarium products, it’s easy to keep a beautiful saltwater, freshwater or reef aquarium. For over 50 years, api has been creating innovative, research-driven solutions that make it easier to care for your fish & aquarium. Api aquarium treatment supplies are designed to work in conjunction with each other to provide best results to control algae, promote healthy bacterial growth & help control & cure fish diseases & conditions such as ich & fin rot. They work to provide a safe, hospitable environment for fish such as tropical community fish, cichlids, goldfish & more. With api, you can spend more time admiring your fish, & less time scrubbing your tank. Make sure to use all products as directed in order to ensure the best results.