My pool numbers show green algae: none; black algae: none and I'm not using any of the hypo stuff you mention. just chlorine. But when I backwash i see slightly dingy water coming out. I get it's kind of milky grey. I have been keeping the chlorine high for two days now ... i put chlorine in at night and by the morning the chlorine reading isn't as high, so not sure if it's the sun or something eating it up. what about the hardness number? does that matter?