What is Mustard Algae and how do I fix it?

What is Mustard Algae?

Mustard algae, yellowish-green or brown in colour, and usually attaches to pool walls and other items including pool equipment, toys and even your bathers. It is usually found in the warmer climates, but mustard algae can grow in all pools. Since it is chlorine resistant, mustard algae can be difficult to get rid of once it is in your pool.

It is worth noting that this pesky nuisance resembles pollen, dirt, or sand. Naturally, most pool owners do not realize they have it.

While mustard algae is not harmful to humans, an overgrowth can attract harmful bacteria like e. coli. What’s more, it can cloud the water and stain the swimming pool. 

How to Get Rid of Mustard Algae

Once you have mustard algae, don’t underestimate it. Here are nine steps to ridding your pool of this seriously irritating problem.

1. Remove all items from the pool.  Rinse pool toys and other items with a chlorine or chloride-based cleaner . Wash your swimsuits and towels separately and thoroughly.
2. Brush the algae and then let it settle. Vacuum it out using waste mode.
3. Balance your pH and alkalinity. Your pH levels should be between 7.2 and 7.4 and your alkalinity should be between 60 and 120 ppm. Balanced water will help the shock work more quickly.
4. Shock your pool with chlorine — twice the amount you would use for a typical shock treatment. (If in doubt drop in to one of our stores with a water sample and we can advise quantities required.) Brush the algae aggressively, which will help the shock destroy the algae from the small crevices on the pool surface.
5. Run the pump and filter 24-hours a day until the algae is gone.
6. Backwash/clean filter media and check your pool. If it hasn’t improved, shock it again.
7. Vacuum your pool to waste to remove any remaining algae so it doesn’t start to grow again.
8. Treat the water with an algaecide.

Mustard algae can be very hard to get rid of once you have it, so the moment you notice it, start treating it. If the first shock doesn’t work, keep shocking. Also, note that it will latch onto swimsuits, toys and equipment, and these items can continue to reintroduce the spores to the pool if you don’t sanitize them well.

If in doubt chat to one of our friendly staff.