Can You Floc a Green Pool? Better Algae Treatment Methods

Tools & Supplies Needed

Find on Amazon: Taylor K-2006C Test Kit , Liquid Pool Flocculent , Muriatic Acid

Quick Answer

Yes, you can floc a green pool, but it's not the best approach. While flocculent will help settle suspended particles and dead algae to the bottom for vacuuming, it won't kill the living algae causing your green water. You'll still need to shock your pool to proper levels first. The SLAM (Shock Level And Maintain) method is far more effective for clearing green pools than relying on flocculent alone.

Why Flocculent Isn't Your Best Option for Green Pools

Flocculent works by binding small particles together so they sink to the bottom where you can vacuum them out. However, a green pool means you have living algae actively reproducing in your water. Flocculent cannot kill algae - it can only help remove dead algae and debris after you've already killed the organisms with proper chlorination.

If you floc without shocking first, you're essentially just temporarily clearing the water while leaving the root cause untreated. The algae will quickly return, often within 24-48 hours, making your efforts largely wasted.

The Right Way: SLAM Method First, Floc if Needed

The most effective approach for a green pool is the SLAM method - Shock Level And Maintain. This process kills all algae and bacteria, then keeps chlorine at shock level until your pool passes an overnight chlorine loss test.

Step 1: Test Your Water Chemistry

Before adding any chemicals, test your pool water for:

• Free Chlorine (FC)
• Combined Chlorine (CC)
• pH level
• Cyanuric Acid (CYA/Stabilizer)
• Total Alkalinity (TA)

Use a quality test kit like the Taylor K-2006C for accurate readings. Pool store test strips are notoriously unreliable for this process.

Step 2: Balance pH First

Adjust your pH to 7.4-7.6 before shocking. If pH is too high, chlorine becomes much less effective at killing algae. Add muriatic acid gradually if you need to lower pH, testing frequently.

Step 3: Determine Your Shock Level

Your shock level depends on your CYA level. Use this FC/CYA relationship:

• CYA 30: Shock level 12 ppm FC
• CYA 40: Shock level 16 ppm FC
• CYA 50: Shock level 20 ppm FC
• CYA 60: Shock level 24 ppm FC
• CYA 70: Shock level 28 ppm FC

If your CYA is above 80 ppm, you'll need to partially drain and refill your pool first, as chlorine becomes ineffective at very high stabilizer levels.

Step 4: Add Liquid Chlorine

Use liquid chlorine (sodium hypochlorite) rather than powder shock or tablets. Add approximately 1 gallon of 12.5% liquid chlorine per 10,000 gallons to raise FC by 5 ppm. Calculate how much you need to reach shock level and add it gradually around the pool perimeter with the pump running.

Step 5: Maintain Shock Level

Test FC levels twice daily and add more liquid chlorine to maintain shock level. Your pool will consume large amounts of chlorine initially as it kills algae. This is normal - keep adding chlorine to maintain your target level.

When to Consider Flocculent

After 2-3 days of SLAM, your water should start clearing but may remain cloudy with dead algae and debris. This is when flocculent can be helpful. Once you've killed the algae and your overnight FC loss is less than 1 ppm, you can add flocculent to speed up the clearing process.

Using Flocculent on a Treated Green Pool

1. Ensure your FC level is at or near shock level
2. Add liquid flocculent according to package directions (typically 1 quart per 20,000 gallons)
3. Run your pump for 2 hours to circulate
4. Turn off pump and let pool sit undisturbed for 8-24 hours
5. Vacuum settled debris directly to waste, not through your filter
6. Backwash or clean filter thoroughly
7. Resume normal SLAM process until overnight FC loss is under 0.5 ppm

Important Safety Warnings

Never mix chemicals directly. Add them separately with the pump running and wait at least 30 minutes between different chemical additions. Always add chemicals to water, never water to chemicals.

Ventilation is crucial when adding large amounts of liquid chlorine. The chlorine gas produced can be dangerous in enclosed areas.

Why This Method Works Better

The SLAM method addresses the root cause of green water - living algae - while flocculent only treats the symptoms. By killing all algae first, you prevent it from quickly returning. The flocculent then serves its proper role as a clarifier for dead organic matter, not as a primary treatment.

Most pool owners who try flocculent alone on green pools find themselves repeating the process multiple times, wasting time and money. The SLAM method, while requiring more initial chemical investment, typically clears a green pool permanently in 3-7 days.

Remember to continue testing and maintaining proper chlorine levels even after your pool clears to prevent future algae blooms.