When green and black algae appear in your swimming pool, it’s relatively easy to treat with shock and filtration, but mustard algae presents a much bigger challenge. This stubborn microorganism is chlorine-resistant, meaning the standard approach won’t help control growth. We’ll show you exactly how to eliminate mustard algae from your saltwater or chlorinated pool!
What is mustard algae?
Mustard algae, or yellow algae, is a type of green algae that thrives in warm, humid climates. Here’s what you need to know about mustard algae before it ends up in your pool:
Where does mustard algae typically grow?
Even though it can withstand normal chlorine levels, mustard algae typically develops on surfaces in shaded areas with poor water circulation, such as:
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Pool walls and floors
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Corners and steps
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Behind ladders and handrails
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Under diving boards
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Around lighting fixtures
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Inside pool skimmers
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On pool toys, floats, and cleaning tools
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In filters and plumbing lines
How do I know if I have mustard algae?
Often mistaken for pollen, sand, or dirt, mustard algae can be hard to identify. Look for:
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Yellow, gold, or brown patches on the walls and floor
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Dusty deposits in shady areas
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Slippery surfaces
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Persistent cloudiness after brushing
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Repeated algae problems despite normal chlorine levels
What does mustard algae do to a pool?
No matter how frequently you clean your pool or balance chemicals, mustard algae will keep coming back until you take the proper steps to eliminate it from the water and all surfaces. Until then, it will increase chemical use, make your pool look dirty, and cause steps, ladders, and floors to become slippery. Long-term blooms can even clog your filter and strain your pump.
How to get rid of mustard algae in your pool
You already know that treatment for yellow algae is distinct from remedies for other types of algal blooms. Here’s a systematic approach to eradicating mustard algae from your pool:
1. Brush and vacuum on the “waste” setting
Begin by scrubbing every inch of your pool with a brush to dislodge the microorganisms from surfaces and break down the protective coatings that safeguard them from chlorine and other sanitizers. You can then vacuum on the “waste” setting to dispose of contaminated water rather than forcing it through your filtration system and risking recontamination.
2. Hyperchlorinate the pool
Use a pool chemistry calculator or follow your test kit instructions to raise free chlorine to a level that’s suitable for your CYA concentration. It’s important to maintain these elevated levels for at least 24 hours while running your pump continuously.
3. Add algaecide to the pool
Once the sanitizer has had time to kill most of the mustard algae in your pool, add an algaecide to eliminate any remaining microorganisms.
4. Clean all your pool equipment
Proper disinfection is essential to your long-term success. Everything that comes into contact with your pool water should be treated, including:
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Pool brushes, vacuums, and automatic cleaners
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Poles and hoses
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Toys and floats
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Swimsuits and towels
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Pool covers
Consider soaking equipment in highly chlorinated water during algae treatment, then rinsing each item and letting it try in the sun. Fabrics should be washed in hot water with a laundry sanitizer.
5. Keep monitoring and adjusting
Test your water chemistry regularly after treatment to ensure free chlorine, pH, total alkalinity, and CYA are within the recommended range. Then, frequently inspect for signs of recurrent blooms and treat again as needed.
How to prevent mustard algae in a pool
After successfully eliminating mustard algae from your pool, the last thing you want to see is a resurgence of dusty yellow patches and slippery surfaces. Here’s how to prevent mustard algae in your pool, hot tub, or spa:
1. Maintain proper chemistry in your pool
Optimal chemical levels are non-negotiable when defending against algae. Ideal readings are as follows:
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Free chlorine: 2.0 ppm to 4.0 ppm
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Total alkalinity: 80 ppm to 120 ppm
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pH: 7.4 to 7.6
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CYA: 40 ppm to 100 ppm
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Calcium hardness: 200 ppm to 400 ppm
2. Schedule regular cleaning and maintenance
While many people choose to clean their own swimming pools, folks who have already experienced a mustard algae bloom may be reluctant to risk another occurrence. Professional cleanings can provide another layer of protection by ensuring that treatments are on schedule, chemicals are precisely balanced, and any signs of algae are addressed right away.
3. Disinfect equipment, toys, and accessories
Your cleaning tools, equipment, and pool accessories can all harbor mustard algae and reintroduce these microorganisms into your pool. Take steps to disinfect all items that may have been exposed to algal bodies, and allow them to dry completely in direct sunlight before returning them to your pool.
4. Shower before swimming
Contaminants in your pool can use up free chlorine more quickly, making your water more susceptible to recurrent blooms. Have all swimmers rinse off before entering the pool to remove sunscreen, cosmetics, sweat, oils, and other impurities.
Keep your pool sparkling clean with GPS Pools!
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