The aquachem kit has not been made in several years. I used to have one. It is similar to the HTH kit but not made by Taylor. It only tested total hardness and used OTO. It idid test CYA. the pH reagent gave false high readings at about 5 ppm FC and the TA test use bromthymol blue indicator so the color chagne from very light blue to yellow was sometimes difficult to read since the colors were so pale.