Yes, you need cya in the water to stop the sun from eating the chlorine. But since we had mostly rainy weather this week I was ok. I did put a puck in the skimmer too, so I used up three which would keep some stabilized chlorine in the water. I have now added some cya to get it up to 30, which will take a while to dissolve. No cya does make the chlorine more effective, but you need at least a cya of 30 to keep the chlorine level consistent during sunny days. Don't worry about total dissolved solids in your pool - it won't bother you once you get the water balanced. Keep up the hard work - it will pay off