Saltwater Aquarium Alkalinity Colorimeter (dKH) Checker HCGet accurate results for your saltwater aquarium with Alkalinity (dKH) colorimeter. The alkalinity colorimeter bridges the gap between alkalinity test kits and advanced instrumentation. Standard test kits have limited accuracy since they rely upon the human eye to match colors. The handheld colorimeter eliminates the hassle of matching to a color chart by providing a direct saltwater alkalinity result in dKH units. The handheld colorimeter is portable