Is this black algae? Or is my 25 yr old pool's gunite plaster wearing off?

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KaZoom

Member
Jan 28, 2024
7
Naples, FL
My pool guy scrubs the pool walls aggressively, but he doesn't scrub the floor. He tells me that I have black algae on the walls which has discolored them. But it seems its only the scrubbed areas that are discolored. Does algae prefer walls over floors?? I'm prepared to treat this as black algae, but if that's not the problem, then I could make the situation worse. I've owned the home for 10 years, and I'd say that the problem has just started in the last year or two.

Also, when we arrived in Dec, for the first time ever, the pool light housing (stainless steel) was entirely black! I wiped it with a paper towel and it came clean. I put some bleach on the paper towel and the black area turned green.

Maybe I have both problems...
Suggestions please!

Here's a pic of the wall.

IMG_3973.jpg
 
KaZoom said:
My pool guy scrubs the pool walls aggressively, but he doesn't scrub the floor. He tells me that I have black algae on the walls which has discolored them. But it seems its only the scrubbed areas that are discolored. Does algae prefer walls over floors?? I'm prepared to treat this as black algae, but if that's not the problem, then I could make the situation worse. I've owned the home for 10 years, and I'd say that the problem has just started in the last year or two.

Also, when we arrived in Dec, for the first time ever, the pool light housing (stainless steel) was entirely black! I wiped it with a paper towel and it came clean. I put some bleach on the paper towel and the black area turned green.

Maybe I have both problems...
Suggestions please!

Here's a pic of the wall.

View attachment 551827
Click to expand...
Kinda hard to tell without water test results from a reliable kit but I don’t see any plaster being worn off. Maybe stains or algae like mentioned above.
 
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That does not look like black algae…

www.troublefreepool.com

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.
www.troublefreepool.com www.troublefreepool.com

gently scrape a sample of the suspected black algae with your fingernail and then smudge it on plain white paper. If the smudge scrapes off and is a greenish color, then it’s black algae.
 
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Is that before you cleaned it or after?

High copper usually causes the filter to be blue.

I see some iron, but not a lot of blue or turquoise, which would indicate copper.

Try the vitamin C.
 

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