A green pool can go from "slightly cloudy" to "swamp" in 48 hours — but the fix is faster than most people think. You don't need to drain the pool. You need to break the algae's grip on your surfaces, kill it, and filter it out. Here's the proven sequence.
Step 1: Brush Everything — Hard
Algae protects itself with a slimy biofilm that chemicals struggle to penetrate. Brushing breaks that shield. Scrub the walls, floor, steps, corners, and waterline with firm, overlapping strokes. An angled brush like the Brustec 15° Scrub Brush reaches the curves and steps where algae anchors first. This step is non-negotiable — skipping it is the number one reason algae treatments fail.
Step 2: Check and Balance Your Water
Test your water and adjust the pH to 7.2–7.4. Sanitizer works dramatically better in this range. If your pH is high, your shock treatment can lose more than half its killing power.
Step 3: Shock the Pool
Apply a chlorine shock at the dose recommended for your pool volume and algae severity — light green water typically needs a double dose, dark green a triple dose. Run the pump continuously while the shock works, ideally overnight.
Step 4: Brush Again, Then Vacuum
The next day, brush all surfaces a second time to dislodge dead and dying algae, let it settle for an hour, then vacuum the pool floor slowly with a manual vacuum like the Delta Wing Vacuum or the MAX 8-Sphere Vacuum. Slow passes matter: rushing stirs dead algae back into the water. If you're new to manual vacuuming, our step-by-step vacuuming guide walks through the whole process.
Step 5: Run the Filter and Clean It Often
Keep the pump running 24 hours a day until the water clears, and clean or backwash the filter whenever pressure rises 8–10 PSI above normal. Dead algae clogs filters quickly — a dirty filter is the most common reason a pool stays cloudy after shocking.
Keep It From Coming Back
Algae returns when brushing stops. A weekly 10-minute routine of brushing and vacuuming — plus balanced water — makes a repeat bloom very unlikely. Stock your toolkit in our pool cleaning collection; orders over $49 ship free.
