Color-Coded Tips for Treating Algae in the Swimming Pool

By November 10, 2020Pool Safety

Written by Jeremy Miller and published on

Algae in the swimming pool is an unwelcome sight, but one that usually can be dealt with effectively. The following “color-coded” tips can help you or your pool service professional identify and eliminate, or at least control, the most common types of algae. It is important to follow manufacturers’ directions for using and storing all pool chemicals.

How to Treat Pool Algae: Tips for Removal & Prevention

There are 4 main types of pool algae that pool owners need to recognize and eventually prevent. The appearance and color of algae is not only a disturbing sight, but an annoying one for pool owners. If at any time you spot this growth in your pool, it is then deemed ‘not swim worthy’ which can put a real damper on your summer plans. In this article, you’ll learn more about the most common types of pool algae and how to treat them effectively.

General Rule: The best way to keep algae at bay is to properly maintain the chemical balance of your pool and water. Make sure that you have an accurate water testing kit to monitor your pool on a regular basis. If you continue to observe the chemical levels in your pool and the water, algae doesn’t have a fighting chance.


Some of you might feel uncomfortable with the idea of using an algaecide to combat green algae. No worries, if you opt out of this method, there is a different way for you to go. The goal is to raise the free chlorine levels high enough so that the algae dies and can no longer grow. To do this, you need to know your cyanuric acid (often called stabilizer or conditioner) level. The higher your cyanuric acid level, the more chlorine is necessary. If your level is too low, the sun’s rays will destroy the chlorine.

It is recommended that you adjust the cyanuric acid levels to the optimum level of 30-80ppm. Once you are finished, shock your pool heavily with (preferably) liquid chlorine or bleach. When shocking, scrub your pool all over to break any algae loose from the walls. Run your filter and clean as needed during this process. The algae are dead when they turn a gray color, but it may take a long time to completely filter it all out. The key to this method is to make sure you have enough chlorine on hand to blast your pool and keep the levels where they need to be.


If you opt to use an algaecide, you can use a copper one that gets the job done fast.To start the process with algaecide, you simply need to shock your pool with a high level of chlorine and circulate your water. Next, you’ll add in the copper algaecide and run the filter for 24 hours. Once the 24 hrs. are up, you will find more dead algae than live algae swimming around in your pool. If they decide to fight back, you will need to repeat this process until they appear grayish in color. After the algae dies, you can utilize a flocculent to sink the algae to the bottom where you can vacuum it out of your pool. Filtering your water should help catch the dead algae as well. Make sure that you clean your filter before you use it to filter algae as it likely contains some level of live algae from the previous circulation.

Green Algae:

The most common free floating type of algae, green algae is relatively easy to get rid of. This type of algae makes your water look clouded and adds a faint green tint to it as well. You might just notice a couple spots here and there, or if it is a particularly pesky variety- it might appear as full on sheets covering larger portions of the pool. If you see green slime, it has arrived. Now, is the time to fight this green foe and below will show you how. If you suspect you might be having an issue with pool algae, check your free chlorine levels. If they are dropping quickly or have dropped quickly, that’s a good sign you’re fighting some algae.

There are two main methods for fighting green algae, both of which are covered below. When fighting algae, no matter which method you choose, it’s important to work quickly and don’t let the green stuff get you down. If you stop before it’s completely eradicated and your free chlorine levels are low, it can grow back like a weed. Make sure you are well stocked on needed pool chemicals and pool supplies before starting either process.

Yellow Algae (Mustard Algae):

This type of algae is also known as a ‘wall clinger’ and typically resides at the shadier end of your pool. Mustard algae is sheet forming and is proven to be very difficult to get rid of completely. If you don’t act quickly, you might have to deal with it for the rest of swimming season. And, no one wants to do that. Yellow algae, much like the weed-grows right back if left untreated.

Black Algae:

Not only is the color ominous, but so is the removal. This type of algae is the most difficult for pool owners such as yourself, to deal with. It is a strong algae with roots and protective layers over the top of the plant. Sometimes it can appear as fully black or even blue with greenish spots. These roots can grow into the plaster of your pool and unless you eradicate it completely; it will simply return in the exact same place. Similar to yellow algae, the black strain can bloom again even if your chlorine and other chemical levels are balanced correctly. The treatment methods are generally the same as for green and yellow algae, but there are a variety of specialized algaecides that help fight black algae in various ways.

Pink Algae:

This algae is also considered a bacteria. It appears as spots or streaks in the corners and crevices of your pool. It spreads slowly and it will rarely bloom the entire length of your pool.

With over 40 years of experience in the business, Doheny’s Pool Supplies Fast has the trusted pool algaecide supplies you need to effectively control algae for good. Say “goodbye” to yellow, green, mustard and pink: with our reliable pool algaecide products, the only color your pool water will be is clear.

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