How to Treat Green Algae in a Swimming Pool
Understanding Green Algae
So, you pull that winter safety cover off the pool after a long hibernation or return from vacation expecting a refreshing swimming spot—only to find a swampy green mess. Fear not! Green algae is a common pool problem, but with the right approach, it can be eliminated.
This process takes time, so don’t expect instant results. For mild cases, you may see improvement in a few days, but for severe algae blooms, it can take up to two weeks.
Step 1: Test and Balance Your Water
If you can see the pool floor, start by vacuuming to waste. If the water is too cloudy, skip straight to testing your pool chemistry. Do not immediately add shock or algaecide—first, balance your alkalinity and pH.
- Alkalinity stabilizes pH, and chlorine is most effective when pH is neutral.
- Adjust alkalinity and pH as needed, then allow the water to circulate for at least six hours (preferably 12).
- Retest after circulation. If levels are still off, adjust them again before proceeding.
Step 2: Shock the Pool and Brush
- Once alkalinity and pH are balanced, it’s time to shock the pool. Raise the chlorine level to 30 ppm.
- Use a high-quality test kit, such as the Taylor test kit, to determine how much shock is needed based on your pool size.
- Never add shock directly to the pool. Instead, dissolve it in a 5-gallon bucket of water before pouring it evenly around the pool.
- Brush the entire pool, focusing on walls, steps, and corners where algae tend to cling.
- The green color should start fading, turning milky white or lighter green as the algae dies.
Step 3: Filter and Clarify
- If your pool is cloudy but no longer green, you’re making progress!
- Test chlorine levels. If they are still above 10 ppm, wait before adding clarifier—high chlorine levels can break it down.
- If you want to speed up the process, consider using Revive!, a flocculant and clarifier that works even in high sanitizer conditions.
- If the pool is still green, add another dose of shock to maintain 30 ppm and brush the pool again.
- Backwash your filter on day three to remove dead algae trapped inside.
Step 4: Vacuum to Waste
- Once the dead algae settle, vacuum to waste to remove debris without clogging the filter.
- If you’re unsure how to do this, check out our step-by-step guide on how to vacuum to waste.
- This step will lower the water level slightly, so be prepared to add fresh water back to the pool.
Step 5: Repeat and Prevent Future Algae Growth
- Continue vacuuming to waste and backwashing the filter daily.
- Once the pool is clear, add a 90-day algae prevention treatment.
- Algaecide is great for prevention but not for treating an existing algae bloom—chlorine is the only way to eliminate it.
- If you skip prevention, you may end up dealing with another algae bloom and needing to hyper-chlorinate again.
How Long Does the Treatment Take?
- Mild cases can clear up in 7-10 days, while severe cases may take up to 2 weeks.
- Allow 24-36 hours for each treatment step to take effect.
- Daily backwashing is recommended during this process to keep the filter from clogging.
Stay Ahead with Regular Maintenance
Now that you’ve tackled the algae problem, consistent water testing and proper chemical balance are your best defense against future outbreaks. By maintaining proper chlorine levels, balancing pH, and using preventative algaecide, you’ll spend more time enjoying your pool and less time fighting algae blooms.
