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Swimming Pool Algae Treatment

Four Day Algae Treatment

Day 1

  • Remove your automatic pool cleaner from the water.
  • Brush the walls and the bottom of the pool. This is important as you need to remove stuck on algae and increase the surface area of the algae you are trying to kill.
  • Adjust the pH to 7.2. Remember, algae thrives in a high pH environment. Also, subsequent chlorination will increase your pH level throughout this process.
  • In the evening, superchlorinate the pool with:

    HTH Extra: broadcast 130g per 10,000 L over a large area of the pool surface, mainly the deep end.


    Unstabilized Liquid Chlorine: use 2 L of liquid chlorine per 10,000 L of pool water. For instance, a 16’ x 32’ rectangle has 72,000 L. This requires 7.2 L of chlorine x 2 L = 14.4 L of liquid chlorine.

Day 2


If water is no longer green, proceed to the next step below - if the water is still green, wait another 24 hours and redo the steps above.

  • In the morning add oxidizer: add 1 kg per 75,000 L of pool water
  • In the evening add concentrated algaecide (40% algaecide): add 100 mL per 10,000 L of pool water

Day 3


The water should have turned from green to a cloudy blue/grey colour. The change in colour means that you have eliminated the algae and can now clean it out of the pool. If the water is still green, wait 24 hours and redo all of the steps above.

  • Add 50 mL of Pool Clarifier per 10,000 L of pool water and let the pool circulate for 12 hours. This clumps the algae together for vacuuming. Shut the pump off and let the cloudiness settle. This can take up to a few days for the very cloudy pools.

Day 4

  • All the algae should be dead and sitting at the bottom of the pool. This dead algae is too fine to be vacuumed through the sand filter. Owners of a sand filter MUST vacuum on the waste setting. Cartridge filter owners can vacuum up the dead algae but be sure to clean the filters afterwards.
  • In the evening, chlorinate the pool with:

    HTH Extra: Broadcast 65g per 10,000 L over the deep end of the pool.

* Add 2 L Container of Phosfree into the skimmer to keep algae from returning!

For more information and other water care products for your Swimming Pool, visit our website at

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