Mustard algae can be a stubborn and frustrating problem for pool owners. This pesky yellow-green algae often looks like sand or pollen and can cling to your pool walls, toys, swimsuits, and equipment. Unlike common green algae, mustard algae is chlorine-resistant and harder to eliminate. But don’t worry! With the right approach and some persistence, you can get rid of mustard algae and keep your pool sparkling clean.
What Is Mustard Algae?
Mustard algae is a type of algae that appears yellowish-green or brown and has a grainy texture. It often grows in warmer climates but can infest pools anywhere. It’s frequently mistaken for dirt, sand, or stains because of its color and texture. While it’s not harmful to humans, mustard algae can attract harmful bacteria like E. coli and cloud your pool water, making it unpleasant and unsanitary.
Why Is Mustard Algae So Hard to Get Rid Of?
Mustard algae is tougher to eliminate than green algae because it is resistant to chlorine. It can survive outside the water on pool toys, swimsuits, and equipment, making it easy to reintroduce into your pool if these items aren’t properly cleaned. Its roots can dig into pool surfaces, especially plaster, making brushing alone insufficient to remove it completely.
Step-by-Step Guide: How to Get Rid of Mustard Algae
1. Identify and Confirm Mustard Algae
To confirm you have mustard algae and not just dirt or stains, scrub the suspected area with an antimicrobial brush. If the algae disperses and turns the water milky, it’s mustard algae. If it doesn’t move, it might be a stain; if it disperses but doesn’t cloud the water, it could be sand.
2. Remove and Clean Pool Accessories
Take out all toys, floats, cleaning equipment, and swimsuits from the pool area. Mustard algae can cling to these items and recontaminate your pool. Wash swimsuits with a color-safe antimicrobial detergent. Clean toys and equipment with a multipurpose cleaner that kills algae but won’t damage your belongings, such as a diluted bleach solution (1 part bleach to 10 parts water). Avoid frequent exposure of plastics to high chlorine concentrations to prevent brittleness.
3. Brush the Pool Surfaces Thoroughly
Turn off your pool pump and brush all surfaces, including walls, floors, and steps, to loosen the algae. Use a wire bristle brush for plaster pools but test a small area first to avoid damage. For fiberglass or vinyl pools, use a nylon brush. Brushing breaks the algae’s protective layer and prepares it for chlorine treatment.
4. Vacuum the Pool to Waste
After brushing, vacuum the debris to waste (bypassing the filter) to remove as much algae as possible from the pool. This step prevents dead algae from clogging your filter and reduces the organic load your sanitizer must handle.
5. Balance Your Pool Water Chemistry
Check and adjust your pool’s pH to between 7.2 and 7.4, and alkalinity between 60 and 120 ppm. Proper water balance ensures chlorine works effectively. Lower pH slightly (around 7.0 to 7.2) to maximize chlorine’s algae-killing power.
6. Shock Your Pool with Chlorine (Multiple Times)
Mustard algae requires a heavy dose of chlorine to kill it. Perform a “shock” treatment by adding about twice the normal amount of chlorine. Some recommend raising free chlorine levels to 15-30 ppm. After shocking, brush the pool again to expose algae hiding in crevices. Run your pump and filter continuously for 24 hours to circulate the chlorine and filter out dead algae.
If the algae persists, repeat the shock treatment until it disappears.
7. Use a Specialized Mustard Algaecide (Optional but Recommended)
Because mustard algae is chlorine-resistant, adding a specialized algaecide designed for mustard or yellow algae can help. Products like “Yellow Out” or other sodium bromide-based algaecides can penetrate the algae’s defenses and improve treatment success. Follow the product instructions carefully.
8. Clean or Backwash Your Filter
Mustard algae spores can lodge in your pool filter. After treatment, backwash or clean your filter thoroughly to remove any trapped algae and prevent reinfestation.
9. Prevent Future Outbreaks
– Maintain proper water chemistry consistently.
– Run your pump and filter for at least 8-12 hours daily.
– Brush and vacuum your pool regularly.
– Clean pool toys and swimsuits after use.
– Use algaecide periodically as a preventative measure.
– Consider using a pool monitoring system to detect early signs of algae.
Tips and Tricks for Success
– Be patient and persistent. Mustard algae is tough and may require several treatments.
– Don’t underestimate the importance of cleaning pool accessories.
– Avoid stirring up dead algae too much during treatment, as it can cloud the water.
– Use a solar blanket or pool cover to limit sunlight, which encourages algae growth.
Getting rid of mustard algae takes effort, but with these steps, your pool will be clear and inviting again.
Mustard algae is stubborn but beatable with thorough cleaning, balanced water chemistry, and persistent chlorine treatment. Keep your pool healthy by staying vigilant and maintaining good pool care habits.