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Help! My Pool is Green!

This tends to be the most common problem for pool owners and is caused by the dreaded Algae. There are over 20,000 types of Algae. Algae are groups of non-flowering plants. They thrive in water, sunlight and warm conditions, exactly what your pool has to offer. Their appearance can vary from green, brown, yellow, or black. It typically thrives in the corners and steps of your pool, the places that circulation is limited.

Green Algae is the most common Algae. It grows on your Swimming Pool and Spa / Hot Tub surfaces. It usually shows up first on the steps of the pool or in corners in very small patches. If you are not sure whether the pool is turning green then run your hands across the surfaces, if it feels slimy then yes you have algae growing. Green Algae can be deceiving because it may appear as a small amount at first and then, in the right conditions, quickly grow over night. The green slime can be removed from the surfaces by brushing but that does not remove the plant from the water. The answer is to “Shock” the Swimming Pool water.

 Shock Treatment:

The best time to “Shock” treat a pool is at the end of the day so that there is less sunlight and the Chlorine has longer to work before the UV rays start burning it off.


Sweep down the walls and the bottom of the Swimming Pool.

Once swept add Liquid Chlorine, this will burn off in approx. 48hrs.

The water may now be cloudy add a Clarifier (Flocculent)

Check the Chlorine and pH levels and adjust as necessary.


Make sure that your pH level is correct (between 7.2 and 7.6), so that the Chlorine can work at its optimum.

Brush the algae from the walls and bottom so that it is all floating free, this enables the “Shock” treatment (Liquid Chlorine) to attack from all sides greatly reducing the time it takes to kill the algae.

Backwash the system. Add Liquid Chlorine, the amount depends on the size of your pool and the amount of algae that you have.

If the condition of the swimming pool does not significantly improve after 12-24hrs of filtering, add a second dose of Liquid Chlorine. You cannot over-shock a pool as it will all burn off in approx. 48 hrs.

Once the algae are dead they will turn white making the water look cloudy. When there is no longer any sign of green in your pool, thoroughly vacuum the pool. It is recommended that you vacuum to waste and not through the filter.

If you cannot vacuum to waste then you will need to backwash or clean the filter to keep it as clear as possible to stop it from clogging and to make sure that there are no live algae spores in there. Algae love it in the filter and will repopulate your pool in no time at all from there.

If the cloudiness won’t go away then add some Clarifier (Flocculent) this comes in Gel Blocks, Tablets, (both of which go in the pump basket) / Liquid Floc or Granular Floc which go into the Swimming Pool water.

It is a good idea to add an Algaecide at this point as a preventative.