This is still one of the most commonly used disinfectants in a swimming pool. Several types of Chlorine Compounds are available. 1. Unstabilized Chlorine A. Calcium Hypochlorite - granular and will not dissolve completely in water. Will tend to leave a lot of residue in the bottom of your pool. B. this Chemical will need to be put into your pool. C. Stabilizer will also have to be added to extend the life of your chlorine. 2. Stabilized Chlorine A. Tri-Chlor - This is the solid form of chlorine and could be either chlorine tablets (3" or 1"), or chlorine sticks. B. Di-Chlor - This is in granular form and is slow dissolving. C. This product line has stabilizer built into it. D. If you use a floater with chlorine tablets, you may need to add some stabilizer because the tablets will not dissolve quickly enough. Chlorine is susceptible to rapid decomposition from the sun's ultra-violet rays. In order to improve the effectiveness of chlorine and reduce its loss, the stabilizer or Cyanuric Acid level will need to be maintained above 40 PPM. The Free Chlorine level of your pool water is what is the most important. That level should be maintained between 1.0-2.0 PPM. Your pool could have a chlorine reading and still have algae because the Free Chlorine level is too low.