Keep your fish healthy and thriving by testing your aquarium water's KH levels regularly with this easy-to-use API CARBONATE TEST KIT for freshwater aquariums. API CARBONATE HARDNESS TEST KIT helps prevent pH problems by stabilizing aquarium pH in fresh and saltwater aquariums. Fast, easy, and accurate testing evaluates KH levels in aquarium water, so that they may be corrected if too low or high. Water with low KH is susceptible to rapid pH shifts, stressing fish and increasing the risk of disease.