Shock the hell out of it.

Add twice the recommended dose of granular pool shock. Brush the walls and floor, run the filter 24/7, and backwash when pressure rises. That’s the fastest way.

Green water means algae has bloomed. Algae die fast with high chlorine levels. Don’t bother with algaecide first — shock does the job if you use enough. A stabilizer (cyanuric acid) helps keep chlorine from burning off in sunlight, but if you already have some in the water, just shock.

You might need to repeat the shock dose the next day if it’s still green. Vacuum to waste if you have that setting — it sends dead algae out of the pool instead of back through the filter. If the water is cloudy but no longer green, that’s good: the algae are dead and the filter just needs time to clear it.

Don’t skip brushing. Algae cling to surfaces. Break them loose so the chlorine can actually reach them.