Run your pump longer and shock it more often.

Yes. Heatwave algae is predictable. Hot sun burns off chlorine fast, and algae loves warm, still water. So you need to outrun it.

Crank your pump runtime to 10–12 hours a day, ideally during the hottest part of the day when chlorine is getting destroyed. That keeps the water moving and filters out spores before they settle. Also bump your chlorine level to the high end of normal — test it daily, because it’ll drop fast. A quick shock treatment at the start of the heatwave buys you a few days of buffer.

Don’t forget to brush the walls and floor once a week. Algae starts as a thin film you can’t see. Disturb it before it gets established. And keep your pH in check (7.2–7.6) because high pH makes chlorine useless.

If you wait until you see green, you’re already in for a scrubbing. Stay ahead of it.