How Do I Get Rid of Yellow or Mustard Algae?
Yellow or mustard algae looks like yellow-brown dust or pollen on the shady walls and floor of a pool. It brushes off easily and comes back within a day or two, and normal chlorine levels do not kill it. To get rid of it, brush the whole pool, shock harder and longer than you would for green algae, clean the filter, and sanitize everything that touches the water, including swimsuits, toys, and brushes.
How do I know it is mustard algae?
- It looks like yellow, tan, or brown dust, not green slime.
- It shows up on the shady side of the pool, on walls, steps, and behind ladders.
- It brushes away in a cloud and returns to the same spots in a day or two.
- Chlorine tests normal, but it keeps coming back.
- Dirt and pollen settle on the floor and do not cling to walls. Mustard algae clings.
How do I get rid of mustard algae?
- Step 1: Test the water, including stabilizer. Bring pH to 7.2 to 7.4.
- Step 2: Put brushes, poles, the vacuum head, hoses, and pool toys in the pool so they get treated too.
- Step 3: Brush every surface, including steps, corners, behind ladders, and inside the skimmer.
- Step 4: Shock in the evening with liquid chlorine and hold chlorine high for several days. Mustard algae needs a higher level than green algae. We will give you a target from your stabilizer reading.
- Step 5: Add an algaecide made for mustard algae if needed. Ask us which one fits your pool.
- Step 6: Run the pump 24 hours a day and brush daily.
- Step 7: Clean the filter thoroughly when the algae is gone. Mustard algae hides in filters.
- Step 8: Wash swimsuits and towels in hot water before they go back in the pool.
Why does mustard algae keep coming back?
It resists chlorine, and it survives on anything that has been in the water. A pool can look clear and still be reinfected by a swimsuit, a float, or a brush that was not cleaned. It also takes hold when stabilizer is high and chlorine is weak, which is common in Bakersfield pools that run on tablets through a long, hot season. Keep chlorine matched to your stabilizer level and brush the shady walls every week.
When should I bring in a water sample?
Bring a sample if the yellow dust returns within a week of treatment, or if you are not sure whether it is algae, dirt, or pollen. We'll check stabilizer, chlorine, and phosphates and help you choose a treatment.
Is mustard algae harmful?
It is not usually dangerous by itself, but it means the water is not sanitizing well, and it can shelter bacteria. Clear it before regular swimming.
Can I swim in a pool with mustard algae?
It is better to wait. You can also carry it to other pools on your swimsuit.
What is the difference between mustard algae and green algae?
Green algae turns the water green and cloudy and dies at normal shock levels. Mustard algae stays on the walls as yellow dust, likes shade, and needs more chlorine to kill.
Is it mustard algae or pollen?
Brush it. Pollen and dirt float away and settle on the floor or in the skimmer. Mustard algae comes back to the same shady spots on the walls.
Don't cry, we can help
Bring a water sample to Top Dog Pool Supply. Local pool owners get a free water test on our Taylor Xpress Flex system, and we'll tell you what to add, and how much, for your pool's size.
Visit us at 7440 District Blvd Suite B, Bakersfield, CA 93313, or call (661) 664-9000. We're open Monday to Friday 9 to 5, Saturday 9 to 4, and Sundays 10 to 4 from April through September.