Whether you're allergic to chlorine or simply don't like using it, there are a ton of alternatives to keep your pool water mold- and bacteria-free.  Ozonators, bromine, and ionizers are good alternatives, though they still contain a bit of chlorine so they're not suitable for those with chlorine allergies. PHMB doesn't have chlorine, and though just as effective, it does cost a bit more than regular chlorine.  You can also use baking soda and saltwater pool sanitizers. The salt level recommendation is usually given by the manufacturers. As for baking soda, use about 1.5 pounds of baking soda per 10,000 gallons of water.