Swimming Pool Algae Removal

Algae  can appear in any pool or spa. They prefer to bloom in shadows but can grow anywhere underwater. Brushing algae alone may not be enough to kill them so I will list here the various steps we use for removing algae.

Note that two different types of algaecides are used. This is done to ensure that the algae are removed in a timely fashion. In most cases, we are hired to remove algae in a pool or spa that we have not had any previous experience with. Our goal is to remove the algae as quickly as possible.

What I used (What you would need to follow the same procedure)

1) A Chlorine and Acid test kit

2) 3 gallons of liquid Chlorine

3) 1 Gallon of liquid Acid

4) Swimtrine Plus Algaecide

5) EZ Clor EZ Clor Granular Algae Out

6) A swimming pool pole

7) Swimming pool net

8) Swimming pool brush (at least one, I used two)

9) Diatomaceous Earth (DE) (Since this pool filter was a DE filter)

1) Check chemicals.

Check the chlorine and PH levels with any standard swimming pool test kit. The chlorine should be at least 3.0 and the PH around 7.2.

Use liquid chlorine to raise chlorine levels and liquid acid to lower PH levels since liquids are the fastest to dissolve in water. (Not sure aboutPH levels? See our PH/Alkalinity guide.)

2) Skim the water of debris.

Skim the leaves with a swimming pool net, branches, grass, palms and any other debris out of the water. These can dissolve into the water, leaving phosphates and/or nitrates behind for the algae to consume.

I use a slit net that catches much smaller pieces of debris. However, this net is more expensive than the average net and is more difficult to maneuver around the water because of its smaller net holes.

3) Use algaecide.
Next, use a liquid copper based algaecide. It won’t get caught in a skimming net and dissolves quickly in the water. Swimtrine Plus was used for this specific job.

4) Brush pool/spa.

Algae has layers and if left alone, the algaecide would need to pass though each layer. When algae are brushed, the layers are reduced, allowing easier access for the algaecide.

I use two swimming pool brushes, a small brush to get in corners, between rock fixtures, and around steps and then a large brush for the sides and floor.

5) Skim again.

Brushing the floor and walls usually stirs up previously unseen debris. These should now be removed from the water.

6) Use second algaecide.

Now, apply a chorine based granular algaecide around the pool/spa. This algaecide will sit an area and slowly dissolve. This is great for concentrating the algaecide on or near algae. I use a chlorine based algaecide since it will also boost the chlorine levels in the water. Since the PH was also just balanced, we know that the chlorine will be at its peak effectiveness. A potassium or bromine based algaecide could also be used, but we stick to what we already know works well.

7) Wait.

The pool/spa needs to filter. Ideally, the system should run constantly for 24-48 hours. The water needs to circulate to mix chemicals and the filter needs to be filtering out dead algae from the water. The pool/spa will change colors from green to grey to clear. The gray is dead algae that will need to be filtered out.

In some cases, the system will be so clogged with algae that it will stop pushing water. The filter will need to be cleaned now and then again after the dead algae is removed from the water.

48 hours later

At this point, the majority of algae will be removed from the water.

8) Clean the filter.

It is now time to clean the filter. In this case, it was a Pentair Quad Filter.

If you need to see a more detailed description of how to do this, see our cleaning filter walkthroughs.

How to clean a Purex Triton 4000 Series DE filter

How to Clean a Hayward ProGrid DE Filter

9) Balance chemicals.

Recheck the chemicals. The chlorine levels will probably be low (under 3.0) from killing algae and the PH will have also dropped below 7.2 from the low PH of granular algaecide.

Use liquid chlorine for raising chlorine levels and soda ash for raising PH levels.

10) Brush pool/spa for the last time.

Check walls and floor; the pool/spa may need to be brushed to remove any remaining dead algae or even vacuumed depending on what your water currently looks like.

There is no way to prevent algae from ever appearing, however keeping the chemicals strong and the pool filtering long enough each day go a long way in keeping algae blooms down to a minimum.