How do I clear green pool water fast?

Add twice the recommended dose of granular pool shock, brush the walls and floor, run the filter 24/7, and backwash when pressure rises. Green water means algae has bloomed, and high chlorine kills it fast — skip algaecide. Use a stabilizer if needed, repeat the shock the next day if still green, and vacuum to waste if possible. Don’t skip brushing, because algae cling to surfaces.