How to Get Rid of Mustard Algae in Your Swimming Pool

If you’ve noticed yellow or mustard-colored patches clinging to the walls or floor of your pool, you’re likely dealing with mustard algae. Unlike green algae, mustard algae is extremely stubborn and can quickly return if it’s not treated properly. It thrives in shaded areas, clings to pool surfaces, and can even survive on pool toys, ladders, and cleaning equipment.

At L&J Pools, we recommend using ProTeam Pool Chemicals for an effective, professional-grade treatment. Here’s our step-by-step guide to eliminating mustard algae and preventing it from coming back.

What Is Mustard Algae?

Mustard algae, sometimes called yellow algae, is a chlorine-resistant algae that often appears as a yellow or brown dust-like coating on pool walls, steps, and corners. It can easily be mistaken for dirt or pollen, but if it quickly returns after brushing, algae is usually the culprit.

Step 1: Balance Your Pool Water

Before treating the algae, make sure your pool chemistry is properly balanced.

Recommended Water Chemistry:

• pH: 7.2–7.6
• Total Alkalinity: 80–120 ppm

Also, clean or backwash your filter to ensure maximum circulation during treatment.

Step 2: Brush the Entire Pool

Thoroughly brush every surface in the pool, paying special attention to:

• Walls
• Floor
• Steps
• Behind ladders
• Corners
• Shaded areas

Brushing breaks the algae loose so the treatment can work more effectively.

Step 3: Treat with ProTeam Mustard & Black Magic

Apply ProTeam Mustard & Black Magic directly to the affected areas.

Recommended Dosage

For severe algae growth, use the higher dosage.

Step 4: Shock the Pool

Immediately after adding Mustard & Black Magic, shock the pool using ProTeam Quick Shock or ProTeam Power Magic.

Dosage:

• 1 pound per 10,000 gallons

This combination helps destroy algae that regular chlorine treatments may leave behind.

Step 5: Run the Filter Continuously

Operate your pump and filter 24 hours a day until the water is completely clear.

Monitor your filter pressure and clean or backwash the filter whenever the pressure rises 8–10 PSI above its normal operating pressure.

Step 6: Brush Daily

Continue brushing the entire pool every day until all visible algae has disappeared.

Consistency is key—mustard algae is persistent and may require several days of treatment.

Step 7: Clean Everything That Went Into the Pool

One of the biggest reasons mustard algae returns is because it survives on pool equipment.

Be sure to sanitize or soak the following items while the pool is at shock level:

• Pool toys
• Floats
• Brushes
• Vacuum heads
• Vacuum hoses
• Telescopic poles
• Ladders (if removable)
• Swimsuits

Failing to clean these items can reintroduce algae back into the water.

Preventing Mustard Algae from Returning

The best defense against mustard algae is consistent pool maintenance.

To keep your pool clean:

• Maintain proper free chlorine levels.
• Test your water regularly.
• Brush the pool weekly.
• Clean your filter as needed.
• Keep water circulating daily.

If you’re already using ProTeam Supreme or ProTeam Supreme PLUS, maintaining 30–50 ppm borates can help improve water quality and support sanitizer performance, making it more difficult for algae to establish itself.

Need Help?

Mustard algae can be difficult to eliminate without the proper treatment and equipment. If you’re struggling with recurring algae or want professional water care, L&J Pools is here to help.

Our experienced technicians provide professional pool maintenance, water testing, algae treatment, equipment repairs, liner replacements, and complete pool renovations throughout Bethel, CT, and the surrounding communities.

Contact L&J Pools today to schedule professional pool service and get your backyard back to crystal-clear condition.

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