How to Get Rid of Mustard Algae in Your Pool—The Right Way

Owning a pool can be one of life’s great pleasures. It’s a refreshing escape during hot summer days and a place for fun and relaxation. However, maintaining a pool comes with its challenges, and one of the most frustrating problems pool owners face is mustard algae. If you’ve noticed yellowish-brown growth clinging stubbornly to your pool’s walls or floor, you might be dealing with mustard algae.

Let’s dive into what mustard algae is, what causes it, and most importantly, how to get rid of mustard algae in your pool the right way.

What Is Mustard Algae?

Mustard algae, also known as yellow algae, is a type of chlorine-resistant algae that can thrive in your pool if left unchecked. Unlike green algae, mustard algae appears as a dusty yellow or brownish film that clings to pool surfaces. It often grows in shaded areas of the pool where chlorine levels are less effective, such as corners, behind ladders, or on the pool walls.

Unlike other types of algae, mustard algae is particularly tricky to eradicate because it’s resistant to many standard pool treatments. This stubborn organism can make your pool look dirty and uninviting, and it can also clog your filtration system if not addressed promptly. If you’ve noticed this stubborn invader in your pool, it’s essential to act quickly before it becomes a larger problem that affects your pool’s overall health and safety.

What Causes Mustard Algae?

Mustard algae can appear in your pool for several reasons, including:

1. Poor Water Circulation: Algae thrive in stagnant water. If your pool’s circulation system isn’t working correctly, you’re providing the perfect breeding ground for mustard algae. Poor circulation means that chlorine and other sanitizers are not distributed evenly, creating pockets where algae can grow unchecked. Regularly inspecting and maintaining your pool’s pump and filter system can significantly reduce the risk of algae formation.
2. Low or Imbalanced Chlorine Levels: Mustard algae is resistant to chlorine, but maintaining the right chlorine balance is crucial for prevention. Inadequate sanitization creates opportunities for algae growth. Regularly testing and adjusting your chlorine levels is essential. Low chlorine levels can occur due to heavy pool use, high temperatures, or poor maintenance practices. Using a high-quality pool test kit can help you monitor these levels more effectively.
3. Warm Water Temperatures: Algae love warm, sunny environments. High temperatures can accelerate the growth of mustard algae, especially during the summer months. Keeping your pool water cool and properly treated during hot weather can help mitigate this issue. Additionally, shading certain parts of your pool or using a pool cover when not in use can limit the sunlight that promotes algae growth.
4. Contaminated Equipment or Swimsuits: Believe it or not, mustard algae can be introduced to your pool from infected equipment, swimsuits, or toys that have been in another contaminated body of water. Always clean and disinfect any items that are brought into your pool to prevent unwanted algae spores from hitching a ride. For example, washing swimsuits in hot water and drying them thoroughly before use can be a simple yet effective prevention method.
5. Neglected Pool Maintenance: Irregular cleaning and maintenance can lead to a build-up of organic debris, which serves as a food source for algae. Leaves, dirt, and other organic materials that accumulate in your pool can quickly become breeding grounds for mustard algae. Adhering to a consistent cleaning schedule will help you stay ahead of any potential problems.

Understanding what causes mustard algae is the first step to preventing its reoccurrence after treatment. By addressing these factors, you can make your pool a less inviting environment for this persistent invader.

Mustard Algae Treatment: Step-by-Step

Getting rid of mustard algae requires a systematic approach. Here’s how to tackle the problem effectively:

1. Brush and Vacuum the Pool Thoroughly
   • Use a stiff pool brush to scrub all areas where mustard algae is visible. Pay extra attention to shaded areas and places with poor circulation, as these are hotspots for algae growth. Brushing helps dislodge algae from the pool’s surfaces, making it easier to remove during the cleaning process.
   • After brushing, vacuum the pool to remove as much algae and debris as possible. If your pool has a manual vacuum, it’s preferable to use it on the “Waste” setting to avoid clogging your filter with algae. Manual vacuuming ensures that the algae is removed from the pool entirely rather than circulating back into the water through the filtration system.
2. Test and Balance Your Pool Water
   • Use a pool test kit to check the water’s pH, alkalinity, and chlorine levels. Adjust the levels as necessary to ensure your pool water is balanced. Aim for a pH level of 7.2 to 7.4 and an alkalinity level between 80 and 120 ppm. Proper water balance not only helps with algae treatment but also improves the overall efficiency of your pool’s sanitizer.
   • Balancing the water chemistry ensures that your chlorine and algaecides work effectively during the treatment process, giving you the best chance of eliminating mustard algae completely.
3. Shock the Pool—Aggressively
   • Mustard algae requires a higher dose of chlorine than usual. Use a pool shock product specifically designed for algae treatment and apply it according to the manufacturer’s instructions. It’s best to shock the pool at night to prevent sunlight from reducing chlorine’s effectiveness. Consider using a double or triple dose of shock if the algae infestation is severe.
   • Shocking the pool raises chlorine levels to a point where mustard algae cannot survive. Be sure to circulate the water thoroughly after shocking to ensure the chlorine is distributed evenly.
4. Use a Mustard Algae-Specific Algaecide
   • After shocking the pool, apply a mustard algae-specific algaecide. This specialized treatment targets chlorine-resistant algae and helps to ensure it doesn’t return. Follow the product’s instructions carefully to maximize its effectiveness.
   • Algaecides designed for mustard algae often contain powerful active ingredients that work synergistically with chlorine to kill algae spores. Using these products as directed can make all the difference in achieving a clean pool.
5. Clean Pool Accessories and Equipment
   • Don’t forget to clean everything that has come into contact with the pool, including skimmers, brushes, toys, and swimsuits. Wash them thoroughly with a chlorine solution to kill any remaining algae spores. Neglecting this step can reintroduce algae into your pool, undoing all your hard work.
   • Cleaning accessories and equipment ensures that no traces of mustard algae are left behind, reducing the likelihood of reinfestation.
6. Run the Pool Filter Continuously
   • Allow your pool’s filter to run non-stop for 24 to 48 hours. This will help remove dead algae and debris from the water. Backwash the filter regularly during this time to keep it functioning efficiently. A clean filter is essential for maintaining clear and algae-free water.
   • Continuous filtration ensures that even the smallest particles of algae are removed, leaving your pool sparkling clean.
7. Re-test the Water and Repeat If Necessary
   • After 48 hours, re-test the water to ensure chlorine levels have stabilized and the algae is gone. If traces of mustard algae remain, repeat the shock and algaecide treatment. Persistence is key to fully eliminating this stubborn problem.
   • Re-testing helps you monitor your progress and ensures that your pool is safe and ready for use once the treatment is complete.

How to Prevent Mustard Algae in the Future

Once you’ve successfully eradicated mustard algae, it’s essential to take preventative measures to keep it from coming back. Here’s how:

1. Maintain Proper Water Chemistry
   • Regularly test and balance your pool’s water to ensure optimal pH, chlorine, and alkalinity levels. Proper chemical levels are your first line of defense against algae. Routine water testing and adjustment help maintain a stable and healthy pool environment.
2. Improve Water Circulation
   • Make sure your pool pump and filter are functioning correctly and run them for at least 8 to 12 hours daily. Consider using additional circulation aids, such as return jets, to target dead zones in the pool. Enhancing water movement helps distribute sanitizers more effectively and prevents stagnant areas where algae can grow.
3. Regular Cleaning Schedule
   • Brush and vacuum your pool weekly to prevent the build-up of organic debris. Don’t neglect hard-to-reach areas where mustard algae tend to thrive. Establishing a consistent cleaning routine keeps your pool surfaces clean and minimizes the risk of algae growth.
4. Use Preventative Algaecides
   • Adding a preventative algaecide to your pool on a regular basis can help keep algae spores at bay, especially during warm months. Preventative algaecides

Why Mustard Algae Treatment Requires Diligence

Mustard algae might be one of the most persistent pool problems, but it’s not impossible to beat. The key is persistence and thoroughness. Missing even one step in the treatment process can allow algae to return, making all your efforts futile.

By understanding what causes mustard algae and following the right mustard algae treatment steps, you’ll not only eliminate this pesky problem but also enjoy a crystal-clear pool for the rest of the season. A clean, algae-free pool is well worth the effort.