Black dust - could be algae - on bottom of pool

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.

Black dust - could be algae - on bottom of pool

Postby alligratorthenyou » Wed 08 Aug, 2012 09:33

i have this black stuff on the bottom of the pool. i dont know if its algae. weve tried everything. it doesnt come off it just sits on the bottom of the pool. we have tried to scrub it off with a hard brush but it scraped the liner. does anyone know what it is


Black dust - could be algae - on bottom of pool

Postby RM » Mon 20 Aug, 2012 17:14

Did anyone find a solution for this? I have the same problem. Small patches that look like dirt and they vacuum or brush away instantly. They come back a few hours later in the exact same spots. I've been running my Salt generator at 100% for 2 days and still can not get rid of them. My chlorine is very high at the moment and I would think Algae would be gone. Any help appreciated.

Black dust - could be algae - on bottom of pool

Postby idieh » Mon 17 Sep, 2012 15:56

Have the same problem with our inground pool. Am told that it is a black algae that is a pain to get rid of.

According to this website, ... -thay.html, there is a way to battle it so am going to try it. Remember dealing with it a few years ago, and had a fantastic pool guy that helped me but didn't remember what I had done and my guy is no longer in business. :(

One thing he always told me was everytime I put liquid chlorine in the pool, was to also put in 1 C of Acid. Needless to say I haven't been the one doing the pool chems and no longer have the same pool guy so it shows.

Good luck everyone
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Re: Black dust - could be algae - on bottom of pool

Postby JIvories » Wed 09 May, 2018 06:37

Ok, this thread is 6 years old, but I have the same problem. Black dust, maybe a kind of algae, that dissipates quickly when you brush or vacuum. Then reappears because too fine for filter. Have people on this list found any solution other than vaccumming it all to waste (which wastes a lot of water and you have to do it repeatedly)?

I think I tried clarifier last year and it didn't work. Is flock the answer, to pull in together, then vacuum to waste or let filter?

Someone could make a lot of money by coming up with the right product for this!
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Re: Black dust - could be algae - on bottom of pool

Postby Teapot » Wed 09 May, 2018 15:26

Black algae is a black coloured bacteria and isn't free floating so what you have is fine silt. How insanely powerful is your pool pump compared to the tiny sand filter I am guessing you have, sizes please.

Slowing down filtration speed can increase your filtration efficiency by around 4x. It can save a truck load of money in electricity to. What I generally do is put a good cotton towel in the skimmer, put the vacuum plate over the lot and vacuum the fine silt up. Pointless if your pump is too powerful as the dirt gets dragged through, gently is better. Full power is ok for backwash but not for filtration.

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