Mustard Algae - Description ?

I have read many posts on the subject of Mustard Algae. Most asking, “Do I have it?”

But find no definitive description to identify it, and I have been unable to find any clear picture of it online.

I did find the following descriptions:

- 1. Appears as yellow powder deposits usually on the shady sides of the walls.

- 2. A yellow film, usually found on steps or walls.

- 3. It is a yellowish-green color and does brush off the walls easily

- 4. A wall clinging variety usually found on the shady side of the pool. It is sheet forming.

- 5. Most often is seen as patches of dark yellow dust that covers various parts of the pool walls and floors. It usually starts in corners of the pool, near the steps, by the ladder, and other areas where the water circulation is not good. Unless the algae gets into cracks, pits or crevices of the pool surface, mustard algae will brush off easily.

What I wish to know is if anyone has positively dealt with this and can give a clear definition from that experience? Also does anyone have a picture?

I often find yellowish dust on the bottom of the pool, never on the steps or wall. Thought this might be Mustard Algae but now thinking it is only fine dirt. Looking to clarify this as I suspect others also make the same misdiagnosis.
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I think one way you can tell is to get some between your fingers and rub - if it feels slimy, it is algae, if it feels gritty it's not.

Also pollen can look yellow, especially if it combines with cottonwood or ragweed "cotton" in the skimmer. They you get a yellow "mat" (for what of a better word) in the skimmer basket. BUT, it doesn't feel slimy, it actually almost feels like shredded cloth. Definitely not mustard algae.

We are also still landscaping around the pool, and the very fine silt that constantly blows in will cover the walls as well as the floor. It looks somewhat yellowish when it is in the pool.

171 views so far and no one is positive they have had Mustard Algae.

The hunt continues !! :)

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I had this and it took me a while to figure out it was mustard algae. These were my symptoms: it grew in shady areas, on a step, on the walls, on a shelf. It was green/yellow color. It would easily brush off only to return in a few days. It seems very resistent to chlorine, I would shock and it would die but then return. It is slimy to the touch. I dind't have a huge chlorine demand with this and my CC was 0 even with the mustard algae. No bloom, the water was pretty clear. I had this problem for quite some time.

Here is how I got rid of it.

Put in a quart/bottle of polyquat 60. Brought chlorine up to 25 ppm with liquid chlorine 12% and held it there for 2-3 days. Ran the pump 24/7 for these 3 days and brushed once or twice a day in the trouble areas. Keeping the chlorine high I think was the key. I tested 2 or 3 times a day and kept it up with the bleach/chlorine. After 3 days I let the chlorine level drop to normal then after it dropped to normal range put in another quart of poly quyat 60. Cleaned the filter. It's been gone ever since.

good luck

Thanks John,

Could you tell me if it was in small patches or a large continuous area ?
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it was mainly in patches. If I let it go long without brushing then it would continue to spread. I have a grotto with a bench and it would grow on that bench, on a step near the beach entry, on the walls in the shade and on a wall in the spa.