hello central cali here with 18k pool. I bought a new home a year and a half ago with a pool and have been learning ever cense. I am not really having problems yet but have noticed a rise in cya this summer. I have a package of bio active already but wont be trying it till probly next week cause of chlorine levels. I know it may not work but I have already purchased it so I am will to give it a try. please note that I am not having major problems with my pool. cya levels are between 150 and 200. they have been on the rise all summer due to chlorine tabs and now this will be an experiment. I will probly go swg if this stuff doesn't work