Maintaining the proper level of chlorine during swim season, adding oxidizer once a week with a 3 to 5 times higher than normal dose of chlorine. Chlorine levels are broken down by the sun's ultraviolet rays. Using cyanuric acid, or stabilizer, to your pool will help you maintain chlorine's efficiency all summer long. Filters remove some particles from pool water, but don't control bacteria or algae. Keep your chlorine level at 1.0-3.0 ppm (parts per million) to eliminate bacteria and/or algae present in the water. Higher levels of chlorine must be kept in order to kill bacteria such as giardia and cryptosporidium.