My pool closing is scheduled for Friday. Water temperature is 65 degrees, which is higher than it usually is this time of year. Unfortunately, I can't change the closing date so I need to know what I can do to prevent algae from developing before the water temperature gets colder. I assume that I need to use polyquat as insurance since water temperature is 65 degrees, so I shocked on Sunday and I'm waiting for the FC to drift down to half-shock level (12 ppm) before adding the polyquat. It looks like I'm going to get to half-shock level a day earlier than anticipated, so I'm wondering if I should bump the chlorine back up to half-shock level (12 ppm) the day before closing before I add the polyquat. If I need to do that, how long do I need to wait after adding the chlorine before adding the polyquat? Also, if the FC dips down below target level after it is added, should I bump it back up to target level (7 ppm) or higher before closing? Last year, when I added the polyquat to 60-degree water at half shock level, it lowered my FC to below target level but I didn't bump it back up. I just want to make sure I know what to do if this happens again. I'd also like to know if there is anything else I can do to prevent algae before the water turns colder. Would it help if I put a few tarps over the top of the cover to block out some of the sun since I have a mesh cover that lets in some light?