How to Clean a Green Pool with 6 Easy Steps

How To Clean A Green Pool

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Clean pools usually have a clear or blue color. However, if not properly maintained, a green color might start to form, making the water cloudy. This is not fun to swim in. Well, if this happens to your pool, all is not lost. You can still restore it to a blue or clear color.

To help you in this, the article explains what causes this green color and gives a step-by-step guide on how to remove it. Let’s get right into it.

Why is Your Pool Green?

The green color is algae and if not checked, this gradually increases to form an opaque deep green that keeps the walls and floor out of sight.

You might be wondering how the algae forms in the first place. This is due to the combination of several factors such as:

  • Not enough free chlorine
  • Temperature above 51ºF
  • Contaminants/debris

That said, for the pool to remain clear, it should be in the following condition:

  • Have a pH of about 7.2-7.6 with the best one being 7.4.
  • Have the correct alkalinity. The ideal TA should be 80-120 ppm.
  • Have enough free chlorine. This is responsible for killing the algae.

Is Algae Toxic?

Algae is actually not toxic if you swim in such water. However, it hosts harmful bacteria such as E. coli, which can cause diarrhea if it gets into your system. Aside from toxicity, algae can reduce visibility in the water and can clog your filters. 

Read More: How to Get Rid of Algae in Pool

How to Clean a Green Pool 

Why is Your Pool Green


Things You Will Need

Step-by-step Guide

1. Remove the Debris

Removing debris is important because algae feed on it. Therefore, eliminating it starves them. However, this cleaning process depends on how intense the algae has manifested in your pool.

If you cannot see 8 inches below the surface, the pool must be drained and then acid-washed. Cleaning the water will not be effective.

However, if you can see 8 inches below the surface, then use the pool cleaner to filter debris, sediments, and algae from the water. If you don’t have this cleaner, use a skimmer or leaf net to trap this debris.

2. Test pH, Cyanuric Acid, and Chlorine Levels

There are various test kits that you can use for this step but we highly recommend the liquid/reagent type over test strips because they are more effective.

That said since algae thrive under low levels of free chlorine, you need to test the pH to see if it is too high. The ideal pH range is 7.2-7.6. If it is higher than 7.6, free chlorine is not as effective because the water neutralizes it. You need to pour in muriatic acid to lower the pH.

As for cyanuric acid, this protects the free chlorine from the sun’s UV rays. Without it, sunlight would break down the chlorine, thereby lowering its level. The level of cyanuric acid should be around 30 ppm. If it is too low, pour in some of it.

As a general rule of thumb, you need 13 oz. of cyanuric acid to raise the ppm by 10 points in a 10,000-gallon pool. However, if the acid level is too high, you need to replace the water or at least part of it.

Finish off by testing for free chlorine to determine the amount that is required for shocking.  

3. Shock the Pool

Shocking is basically super chlorination. This process involves pouring in a large amount of chlorine (determined after testing) to kill the algae. Since the process might require several pounds to adjust the chlorine level, we recommend buying a large quantity, say 25-30 lbs.

You can also use liquid chlorine and this might require 3-4 gallons per day until you get the desired results. That said, liquid chlorine works faster than the granules because it dissolves faster in water. We recommend using this for quicker results.

Read More: When to Shock Your Pool

4. Brush, Pump and Filter the Pool

Chlorine takes some time to work its magic but after about a day, you will notice the green is gone and cloudiness has kicked in. This should not worry. It is actually a good sign because it is caused by dead algae.

The pool’s filtration system should handle this easily as the water is pumped and circulated through. You can also run the pool cleaner to work hand-in-hand with the pump and filtration system to quickly get rid of the cloudiness.

As this goes on, brush the walls, steps, and ladders to loosen any algae (dead or alive) so that it is filtered out.

5. Test for Overnight Chlorine Loss

UV light and algae are the ones responsible for depleting free chlorine at this stage. Therefore, to check if the water still has algae, you need to test the chlorine loss overnight. This eliminates sunlight loss from the equation.

A loss in chlorine means the water still has algae and shocking should continue. Repeat this every night until you test no drop or a very insignificant drop. Once this happens, let the chlorine drop to the target level and that’s it.

6. Continued Maintenance 

Clearing out algae from your pool is quite a lengthy process that might take days. To avoid all this, you should actively maintain the water by testing it and applying all the required chemicals on time.

We strongly suggest the use of pool cleaners such as the robotic, pressure-side, or suction-side type. This will ease pressure on the pool’s filtration system and make it easier to scrub the floor, walls, and steps.


In summary, green pools should not cause you to worry too much. However, it will take a lot of work and patience to restore the water to be clear and transparent. Following the steps above should ready your pool for swimming in a few days.