How to Kill Black Algae in Your Swimming Pool

Algae are plants that grow in water that is not properly sanitized and they feed on sunlight and minerals in the water. Among the existing types of algae, the hardest to get rid of is the black algae because it usually grows in colonies and unless you kill it at its root, it will continue to grow and affect your pool. What is even worse about it is the fact that it will not only appear on the bottom of the pool but also in the plaster or concrete. In case it is not removed, the algae can seriously damage the pool, and although you may follow the right steps to sanitize the swimming pool, it can still grow and develop. Therefore, in case you have noticed this appearance in your pool and you want to know the exact steps to efficiently kill black algae, read the lines below and see what you have to do to eliminate this risk.

Clean the Filter

Since it has made its appearance in the pool, it is also possible for it to be present in the filter, so it is recommended that you clean the filter thoroughly. Also, besides the filter, it is wise to clean the pool equipment so that any possible algae to be removed and to prevent its reappearance.

Brush the Affected Areas

The first step you have to take is to brush the areas affected by the black algae with the help of a brush that is specially designed for your type of pool. You have to do this in order to remove the protective cover of the algae so that the chemicals used can effectively destroy the roots. Therefore, you have to firmly brush the affected areas and if necessary you can repeat this procedure for more than one time. However, make sure that you sterilize the brush after using it because it can easily grow on it.

Use a Chlorine Tablet to Scrub the Affected Areas

After you finish brushing the pool, you can use a broken chlorine tablet and scrub all the affected areas to increase the chances of killing the unwanted mold. This procedure may require more time, but you should try to do this if you want to achieve the best results.

Add Algaecide on the Affected Areas and in the Water

This is another important step you have to take because although the algaecide does not actually harm the black algae, it helps the chlorine do its job by eliminating the protective shield of the contaminant. Therefore, add it in the areas affected by the algae, and then in the water, and let it sit overnight for best results.

Shock the Pool

By shocking the pool you will be able to sanitize your pool and eliminate the existing algae. The most efficient way to this is to add 3 pounds of chemicals per 10,000 gallons after the sun goes down in order to prevent the UV rays from altering the chemicals in the pool. After that, you have to let the treatment for 24 hours while turning the pump off. During this time, you can brush again the pool, offering a special attention to the areas which were affected by the black algae.

Vacuum the Pool

Vacuuming the pool after the previous steps will help you perform the normal cleaning task, but it will also help you eliminate the dead algae. In this way, your pool will be clean and you will be able to eliminate any existing dead particles. To make your work less tiring, what we recommend is for you to invest in a robotic pool cleaner that will handle vacuuming the surfaces of the pool for you. Best of all, this type of cleaning robot can handle filtering the water of the pool as well, thus both the surfaces and the water will be clean and free of debris of all kinds. Therefore, the chances for this problem to appear will be greatly reduced. Just program it to start cleaning the pool on a daily basis, and you won’t ever have problems of this kind.

Repeat the Process if Necessary

In case you notice that black algae are still present in the pool, it is recommended that you repeat the entire process until you achieve the desired results. As we have mentioned before, removing it is quite difficult and it usually requires more time until it is completely eliminated.


  1. Dimitri says:

    I had these types of issues for a long time, no matter what I did, the problem coming back. But since I bought a robot pool cleaner and set it to clean the pool daily, I haven’t had problems with black algae. This is the solution that I recommend to others as well as it’s the only one that has worked for me.

  2. Barry says:

    I tried out the advice given in this article, and it worked for me. Thank you, now I can finally use my home pool again safely!

  3. Jacob says:

    Will shocking the pool regularly help prevent the appearance of black algae? I had this problem in the past, got rid of it, and I’m wondering if this is a good prevention method.

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