What to Do If Your Pool Water Turns Green OvernightUpdated a month ago
A green pool overnight is almost always an algae takeover—thanks to Australia’s warm temps, low chlorine, or a storm stirring up spores. Don’t panic! Here’s how to turn green to clean, and restore clarity fast.
Step 1: Test & Balance Water
Check chlorine: Likely 0 ppm (algae consumes chlorine rapidly). Use chlorine shock to get your chlorine levels up to where they need to be.
Adjust pH to 7.2–7.4 (low pH boosts chlorine’s effectiveness).
Test stabiliser (CYA): If >80 ppm, partial drain may be needed.
Step 2: Shock the Pool
Use calcium hypochlorite shock (strongest option):
Dose: 1kg per 10,000L (double for severe algae).
Pour around the pool edges at dusk to avoid UV burn-off.
Saltwater pools: Boost chlorinator to maximum output and add liquid chlorine.
Step 3: Brush & Scrub
Brush walls, floors, and corners aggressively to break up algae biofilm.
Focus on shaded areas (algae thrives where chlorine can’t reach).
Step 4: Run the Filter 24/7
Backwash/clean filters every 4–6 hours (clogged filters won’t clear algae).
Add clarifier to clump dead algae for easier filtration.
Step 5: Vacuum to Waste
Once algae settles, vacuum debris directly to waste (bypass the filter).
Top up with fresh water afterward.
Step 6: Prevent Regrowth
Maintain chlorine at 3–5 ppm for 3–5 days post-treatment.
Add algaecide to kill lingering spores.
Use a phosphate remover to starve algae.
When to Call a Pro
Green persists after 48 hours (could indicate mustard algae or metals).
Suspicion of broken equipment (pump/filter failure).
Need Algae-Killing Gear?
Grab chlorine shock, algaecide, or phosphate removers for a quick fix. We also have a green algae chemical bundle that contain everything you need to deal with green algae in a snap.
Final Tip: Green pools love neglect—stay vigilant with weekly testing and shock after heavy use.