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How to Get Rid of Mustard Algae in a Pool

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Mustard or yellow algae is a rare form of pool algae that is more common in warmer southern areas, but that doesn’t mean your pool won’t be infected. It’s important, that if you spot signs of mustard algae, to act quickly and get rid of it.

How to Get Rid of Yellow Algae in a Pool

What is Mustard Algae?

Mustard algae is rare and often mistaken for sand, dirt, or a stain in your pool. It’s not slimy like regular green algae, but it likes to attach itself to pool walls and other items.

It’s also chlorine-resistant and very stubborn. It can even live outside of your swimming pool. That means pool equipment, toys, floats, and even bathing suits. If you have mustard algae, you’ll want to disinfect these items right away.

How To Kill Mustard Algae in 10 Steps

Here is a simple step-by-step guide to getting rid of the algae.

1. Machine Wash Your Suits

Wash all your bathing suits in the washing machine and dry in a dryer. This should kill the algae if it has infected these items.

2. Clean Your Toys and Floats

Disinfect all toys and floats with a chlorine based solution. Clorox cleaner with bleach If you click this link and make a purchase, we earn a commission at no additional cost to you. should work just fine in this case. You don’t want to bleach your toys and floats.

Clorox Clean-Up Cleaner with Bleach Spray - 32 oz. Price: $10.89 If you click this link and make a purchase, we earn a commission at no additional cost to you.

3. Move Equipment to Shallow End

Place all maintenance equipment, including hoses and poles, in your pool (the shallow end, if you have one). When you treat the pool with shock If you click this link and make a purchase, we earn a commission at no additional cost to you. , this will sanitize all your equipment. You can also throw anything you think might be infected with mustard algae in the pool.

In The Swim Chlorine Pool Shock - 1 lb. - 12 pack Price: $39.99 If you click this link and make a purchase, we earn a commission at no additional cost to you.

4. Vacuum The Algae OUT

Fill up your pool with fresh water to the very top. Hook up your manual vacuum cleaner If you click this link and make a purchase, we earn a commission at no additional cost to you. (do not use an automatic vacuum for this) and turn your filter to waste, not backwash.

Mustard algae can live in your filter, so you don’t want to vacuum the algae through your system. Since you are vacuuming the water directly out of your pool, you are going to lose some water. That’s why recommend filling your pool up to the top, before you vacuum, to compensate for water loss.

Hayward Pool Vacuum Cleaner Head Price: $40.31 If you click this link and make a purchase, we earn a commission at no additional cost to you.

5. Test Your Water

Make sure your pool water is properly balanced using test strips If you click this link and make a purchase, we earn a commission at no additional cost to you. . Your pH levels should be between 7.4 and 7.6 and your alkalinity should be between 120 and 150 ppm (parts per million). This will allow the shock treatment to be more effective.

AquaChek Select 7-in-1 Pool and Spa Test Strips Complete Kit Price: $12.87 If you click this link and make a purchase, we earn a commission at no additional cost to you.

6. Brush Your Pool

Brush the algae off your pool walls and floor using a algae brush If you click this link and make a purchase, we earn a commission at no additional cost to you. . Also, brush the entire pool. You want to break up the algae and get it in suspension so that the chlorine from the shock can attack and destroy it.

Poolmaster Algae Brush with Stainless Steel Bristles Price: $19.43 If you click this link and make a purchase, we earn a commission at no additional cost to you.

7. Triple Shock Your Pool

Just like a regular algae-killing treatment, you want to shock If you click this link and make a purchase, we earn a commission at no additional cost to you. the heck out of it! Three pounds per 10,000 gallons of water. Make sure you shock at dusk or nighttime, and leave your filter and pump running 24 hours a day until the algae is gone.

DryTec Calcium Hypochlorite Shock - 1 lb. - Pack of 24 Price: $64.38 If you click this link and make a purchase, we earn a commission at no additional cost to you.

8. Keep Brushing

Keep brushing your pool for the next couple of days. It’s a good idea to keep your pool properly sanitized during this time.

Keep checking your pH and alkalinity levels to make sure they stay in range. You want to keep that algae from attaching itself to anything, like the walls and floor of your pool. If the algae is in suspension, you will have an easier time killing it.

9. Make Sure It’s Safe

After a couple of days, if the algae seems to be gone, it’s safe to take any toys, floats, equipment, and bathing suits out of the pool.

I would suggest shocking your pool one more time for good measure. It doesn’t have to be a triple shock, you can just use one pound of shock per 10,000 gallons. Just make sure your filter is still running and you shock at night or dusk.

10. Check and Repeat

After you’ve done your final shock treatment, it’s time to test your water If you click this link and make a purchase, we earn a commission at no additional cost to you. and repeat if needed.

If the water chemistry is good and the water looks clear, then you should be fine for now. If, however, the pool water isn’t chemically correct, be sure to get it back where it needs to be.

How To Prevent Yellow or Mustard Algae from Growing

Keeping your pool properly balanced and sanitized is the key to keeping all forms of algae from growing. Make sure you:

Happy Swimming!

Recommended Reading

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We cut out all the fluff and confusion of pool maintenance and stripped it down to the bare bones in this easy-to-read illustrated digital guide.

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Last Updated: Sunday, July 28th, 2013