A Complete Guide to Eradicate Mustard Algae from Your Pool Efficiently & Effectively

Mustard algae is a common problem that many pool owners come across. You may be asking yourself how do I get rid of mustard algae in my pool? Well, this article will tell you everything you need to know about mustard algae…

You know those slimy, clingy yellow monsters that lurk in your pool-they are not only gross, but they also give off a very obnoxious odor.

You might think about giving up on swimming altogether, but don’t worry! There are many ways to repel and get rid of these icky blobs. Let’s explore this topic together, shall we?

What Is Mustard Algae?

Mustard algae is a form of yellow algae that can grow in any freshwater setting, including the water supply of pools and hot tubs. If you notice an increase in your chlorine consumption, you may be dealing with mustard algae. It often has a pungent odor and usually grows in colonies that resemble bright yellow-green scum.

Mustard Algae

It thrives best near the top of the pool’s water and can quickly accumulate at concentration levels higher than what other types of algae would tolerate. Though mustard algae don’t pose any significant health risks, it disrupts the overall cleanliness and aesthetic display for those swimming in pools with it present.

Mustard algae love to attach themselves to pool walls and other objects, which is a concern because they may also live outside your swimming pool. Swimming pool equipment, pool toys, floats, and even bathing suits are vulnerable to this nefarious little customer.

If you have even the slimmest suspicion that your pool may be infested with mustard algae, you’ll want to have your disinfectant close at hand.

Who or What Is the Source of Mustard Algae?

Typically found in warm regions, mustard algae is a freshwater organism that thrives in warm areas. The tiny cells of algae often move into pools on the suits, hair, or water toys of individuals who have dragged them into lakes and rivers in their cars or on their bodies.

It may also spread from one pool to another, particularly if the same pool equipment is used in several pools without being adequately sterilized in between.

Mustard Algae

What Does Mustard Algae Do in a Pool?

Mustard algae is a troublemaker. It can cause a build-up of sediment within a pool, leading to clogging of filters and decreasing the effectiveness of chlorine.

In the worst-case scenario, a yellow algae infestation produces an environment for bacteria and germs, such as E Coli, which may be hazardous to a person’s health.

To put it another way, if you have this algae in your pool, you must take immediate action to eliminate it.

When and Where to Look For Mustard Algae

To get rid of mustard algae, you must know what it looks like so that you can identify where it’s hiding; otherwise, it could take weeks or months to find the right spot to remove. There are several ways that you can uproot this nasty little pest!

Mustard algae (also known as yellow algae) is distinguished by its unique yellow hue, ranging from a brilliant yellow to a darker mustard yellow. It has a dry, powdery appearance and is often mistaken for dirt or pollen.

This kind of algae loves shade and still water; therefore, it is more likely to be seen clinging to the pool’s sides or bottom. Although mustard algae may survive in pools with enough sunshine and adequate water circulation, the microscopic cells of the algae can grow in small “dead” places, shadowed regions under ladders, and tiny cracks where they can find the protection they need.

How to Get Rid of Mustard Algae That Infested Your Pool

The icky, yellow blobs that make pools smell bad are not easy to get rid of.

Mustard algae love shady, hidden areas like the pool filter, the rungs of ladders, and around the lights. Luckily there are many ways to drive off and get rid of them! Below, you can read about tips for getting rid of mustard algae:

1. Decontamination is one of the best ways to get rid of mustard algae. Therefore, it is highly advised that you decontaminate your pool water and other equipment immediately after discovering this kind of algae to stop it from spreading.

2. It’s also important to always have fresh filters on hand to minimize the risk for additional infestation. Your pumps should also function properly to force out any sludge and sediment that might harbor potential yellow invaders.

3. Brush the algae rigorously and then let it subside. Use the waste mode of your vacuum to clear it out.

4. pH levels should be between 7.2 and 7.4, while alkalinity levels should be between 60 and 120 parts per million (ppm)—balanced water aids to the effectiveness of the pool shock.

5. Chlorine shock your pool by adding double the quantity of chlorine you would normally use for a shock treatment. Brush your pool excessively because this will aid in the shock’s ability to kill any algae accumulated in tiny cracks on the pool surface.

6. Continuously run the pump and filter for 24 hours each day until the algae are eradicated.

7. Backwash and clean the filter media, then inspect your pool. If the situation has not improved, shock it once again.

8. Vacuum your pool to waste to eliminate any leftover algae and prevent it from growing again.

9. Make sure to use an algaecide to treat the water.

Preventive Measures for Mustard Algae

You must maintain your pool maintenance to avoid the growth of mustard algae.

Here are six tips for preventing mustard algae growth.

1. Test your water chemistry regularly to ensure that the pH and alkalinity are in acceptable ranges with this kits.

Mustard Algae - Test your water chemistry

2. Keep running your pump filter for at least 12 hours a day to prevent algae growth.

3. Maintain the cleanliness of your pool by vacuuming and brushing it regularly.

Mustard Algae - Pool vacuuming

4. Make sure to use trusted sanitizer, and if you’re using chlorine, keep a proper chlorine level.

5. Shock your pool with either a non-chlorine or a chlorine shock once a week.

Mustard Algae - Chlorine shock

6. You can also use a robotic pool cleaner to help you out clean the pool surface.

Frequently Asked Questions (FAQs)

What is mustard algae and how does it differ from other types of algae?

Mustard algae is a yellowish-green or brown algae that commonly forms on pool surfaces. It’s often mistaken for dirt or sand due to its fine texture. Unlike other algae, it can cling to pool surfaces even when brushed.

How does mustard algae develop in pools?

Mustard algae can enter the pool through rain, wind, swimsuits, or contaminated pool equipment. It thrives in poorly maintained pools with imbalanced water chemistry, inadequate sanitizer levels, and insufficient circulation.

What steps should I take to eliminate mustard algae from my pool?

Eradicating mustard algae involves several steps. Brush pool surfaces thoroughly to break up the algae colonies. Shock the pool with a chlorine shock treatment, and ensure chlorine levels are maintained high for a few days. Vacuum the pool to remove dislodged algae, and clean or backwash the filter.

Can I prevent mustard algae from returning after treatment?

Yes, preventing its return is crucial. Maintain proper sanitizer levels, balanced water chemistry, and adequate circulation. Regularly brush pool surfaces to prevent algae from attaching. Adding an algaecide specifically designed for mustard algae prevention can also help.

Is it safe to swim in a pool with mustard algae?

While mustard algae isn’t harmful to swim in, it can make pool surfaces slippery and aesthetically unappealing. It’s recommended to address and eliminate mustard algae promptly to ensure a clean and enjoyable swimming experience.


Mustard algae may be tough to get rid of after it has taken hold. Therefore it is important to treat it as soon as you detect it. If the initial shock does not work, keep shocking until it does the trick.

Also, keep in mind that it will attach itself to swimsuits, toys, and pool equipment and that these things may continue to reintroduce the spores into the pool if they are not properly sanitized.

To get rid of mustard algae (also known as yellow algae), you must fight it from every angle possible. So bring out your furry and start scrubbing with vengeance.

Looking for more helpful tips and tricks to ensure your pool is safe, clean, and functional? Look no further! Here’s a list of articles with all the answers. Visit our website to learn more about pools.

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About the author

Brian Anderson

The rather dry pool world out there is in need of some passion to make it shine. With the help of my son Ruben and his wife Maria our mission is to help you create the favorite spot of your house - your pool.

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