How to Get the Green Off of the Bottom of a Pool

A green swimming pool brings down the overall appearance of your backyard.
A green swimming pool brings down the overall appearance of your backyard. (Image: Thomas Northcut/Lifesize/Getty Images)

No matter how well you take care of your pool, green on its bottom can make it look poorly kept. Green algae are the most common cause of a green pool bottom, according to Poor filtration or simply Mother Nature blowing green algae spores into the pool water can cause algae to grow. No matter how the algae enter the pool, they will take over the sides and leave sheets of slime on the pool’s bottom surface in a short amount of time.

Things You'll Need

  • Nylon or steel pool brush
  • pH test strips
  • Hypochlorite
  • Pool testing kit
  • Algaecide
  • Pool vacuum

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Scrub the sides and bottom of the swimming pool using a nylon brush for vinyl pools or a steel brush for plaster-surfaced pools.

Test the pH of your pool to make sure it is between 7.2 and 7.6 so that the algaecides will react properly. Adjust your pool's pH level until it ranges from 7.2 to 7.6.

Add enough hypochlorite to your pool for the water to turn cloudy and gray. Brush the bottom of the pool again, this time pushing the green algae toward the drain.

Backwash your pool's filter once the pressure gauge reads 8 to 10 lbs. past the clean limit. Test the chlorine limit of your pool to make sure that it is lower than 5 ppm, or parts per million, with a pool testing kit. Do not proceed until the chlorine level is below 5 ppm.

Brush the algae from the bottom of the pool again and add algaecide specifically made for green algae. Let the algae and algaecide settle at the bottom of the pool. Turn on your pool vacuum and allow it to suck up the algae sitting on the bottom.

Backwash the pool filter once more and test the pool water. Adjust the chlorine levels as needed to bring them back to the specifications indicated in your pool's instructions. Change the pool’s filter to remove any algae contamination.

Tips & Warnings

  • If algae continue to come back, your filter may be contaminated. In that case, you need to drain your pool completely, perform an acid wash on the surface and change the filter cartridge to remove all traces of algae from the pool.


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