How to Get Rid of Mustard Algae in a Pool


We need to know what mustard algae is in order to recognize it in the water when treating your pool.

Mustard algal may be yellowish, yellow-green, or brown, and it’s usually slimy.

Mustard algae is frequently mistaken for dirt or sand and will cling to pool surfaces, light fixtures, wall fittings, ladders, and other objects such as toys or bathing suits.

Mustard algae thrive in temperatures between 60 and 90 degrees Fahrenheit, though it can grow in any pool. Mustard algae is common in most pools, and without constant care, any pool surface can get it. Because mustard algae is chlorine resistant, eradicating it once it has established itself in your pool might be more difficult than other algae.

Mustard algae can quickly spread from pool surfaces to other objects in the pool. While mustard algae may be brushed and scraped off, you’ll want to treat the water, surfaces, and objects properly in order for it not to return.

What You Need to Know About Mustard Algae Prevention

Prevention is always better than cure. The good news is that mustard algae are preventable.

The first step in preventing mustard algal growth on your pool surfaces is to take proactive water care measures.

Follow the instructions for pool and spa care given below to prevent mustard algae infestations:

Balanced pool water chemistry

1. Maintain balanced water chemistry.

Unbalanced pool water chemistry can wreak havoc on its surfaces and equipment. Keep the pH, alkalinity, calcium hardness, cyanuric acid, and other water parameters in check by testing them on a regular basis

2. Use the right filtration processes.

Impurities can build up if your system isn’t properly filtered, posing a higher risk for mustard algae to grow. Make sure your filtration equipment is running for at least 12 hours each day. With an energy-efficient variable-speed pump, we recommend 24-hour circulation with a variable speed.

4. Remove any debris and contaminants from your surfaces.

Brushing and vacuuming your pool surfaces on a regular basis is essential. Brushing the pool is critical to keep mustard algae spores from growing on the surface.

4. Use sanitizer

Keep a measurable level of sanitizer like chlorine in your pool water.

5. Circulation

The removal of particles and debris from your pool water is assisted by circulation. Your pool’s sanitation system, filter, and added chemicals won’t operate correctly if there isn’t enough circulation. Check for any dead zones in your pool’s circulation and make any necessary adjustments to the wall return jet fittings.

6. Algaecide

This is where I would personally start. Algaecides are a highly effective and fast-acting method to keep your swimming pool water clear of algae. Make sure to use an algaecide proactively once per week in order to prevent and eliminate algae blooms.

7. Filtration

Backwashing your pool is an important procedure in maintaining clean pool water. Send water backward through the filter to remove any particles and keep it running smoothly, but do so according to the manufacturer’s directions precisely. If you have a high degree of organic loading, you may need to backwash your pool more frequently.

How to get rid of Mustard Algae

If you suspect that your pool has a mustard algae outbreak, you’ll need to take action right away. Here are some step-by-step instructions on how to get rid of a mustard algae.

1. Remove all items in the pool

Remove all items that aren’t connected to your pool, such as toys, floats, and other attachments. If you don’t clean these objects properly, the spores can be reintroduced to your water if they aren’t sanitized.

Remove any obvious debris, such as stones and other particles. If your items have been outdoors for an extended period of time, you should clean them with a mild soap and water so that mold does not grow on the item. To thoroughly disinfect your things, use a multipurpose cleanser to destroy mustard algae without damaging them, such as a multi-purpose cleaner. Because bleach or cleaners containing bleach may cause your objects to discolor and are not suggested, be careful about using it. To wash away any mustard algae in your swimsuits, use a normal laundry detergent.

2. Brush it off

Turn off the pump and clean all of your pool and/ surfaces. The next step is to vacuum up any mustard algae debris that has fallen into the pool or onto the spa floor using a vacuum. Brushing will help release the mustard algae so that the shock can destroy it and collect it.

It’s also advised to use a wire bristle brush, however be sure there won’t be any damage to the plaster. Please note that only regular nylon brushes can be used on fiberglass and vinyl liner pools. If the two methods of vacuuming listed above are not an option, clean the filter using the basic vacuum process. Mustard algae may also grow in the filter; therefore, a complete backwash or cleaning of it will be necessary.

3. Check and balance the water in your pool.

If your pool is not balanced, the chlorine shock won’t work properly. The water must be pH 7.2 to 7.4 with an alkalinity level of 60 to 120 ppm in order for the chlorine shock to operate correctly. In order for optimum performance, make sure your outdoor pool’s acid levels range from 20 to 40 ppm.

4. Shock

pool schock for mustard algae

The procedure of adding significantly more chlorine to the pool water than is required is called shocking. The chlorine may “burn” through difficult substances, chemicals, oils, and strong types of algae shock. We recommend using calcium hypochlorite, such as cal-hypo granular, or sodium hypochlorite, such as liquid bleach to shock your pool. Add your shock to the water at dusk or at night and leave your filter and pump running 24 hours a day until the mustard algae is gone to get the most out of it. Remember that usually, mustard algae can be eradicated if the dose of shock is 10 ppm.

5. For a few days, use these techniques to maintain the water balance.

Continue to check and balance the water for a few days after the initial shock. Because of the large amount of chlorine used, the water’s chemistry will be altered, so be careful to restore it to its proper state. Also, continue to clean the pool as usual for a few more days.

If any mustard algae has regrown, repeat the procedure immediately. Even if the concentration of shock is set at a moderate level of 10 ppm, it’s still essential to eliminate the mustard algae. When the treatment is completed, backwash and/or clean the filter media and apply an anti-algae medication to finish off with.


By following the tips and advice given in this article, you can get rid of mustard algae in your pool quickly and easily. Mustard algae is not as easy as normal gree algea to get rid of so make sure you read follow the advice provided in this article. If you need help with your mustard algea problem, call the pool professionals.

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