Aquarium Systems Test Kit A new range of test kits from Aquarium Systems that accurately test your pond/aquarium water. Aquarium System\'s Seatest KH, or buffering capacity, test kit, comprising x2 10ml carbonate hardness indicator reagent liquids. Bicarbonates buffer your aquarium water against PH changes, which vary according to various biological processes within the tank; measuring the KH levels will indicate when stabilising measures are required. Please note this product is short dated - BBE August 2015.