I add the Tech CB for Calcium and buffer. I have alittle over 100gals of water in my reef with sump. I like to keep my Cal. at 450-500ppm. and my Dkh at 10. To maintain this value I add 20cc a day of Part A and 20cc of Part B. If I wish to raise the Cal I would add 25cc of Part A. Wish to Raise DKH add 25cc of part B. I also add Tech I for Iodine, as well as Strontium & Molybdenum.