Black Algae

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
I'm new here
I'm new here
Posts: 6
Joined: Wed 18 Nov, 2020 17:45
My Pool: AGP 25,000 gallons 31' x 20' plus Spa 8' x 5.5' (3 jets)
Polaris 280; Booster Sweep Pump .75 HP
Hayward (A.0. Smith) Single Speed Pump 1.5 HP RPM 3450 SF: 1.33 FR: 56JPH: 1 Type: UAK
Hayward W3S270T Pro-Series Glass Filter, 27-Inch
From pump to closest end of pool is 22'
Pump is same elevation as pool
Plumbing size is 2"

Black Algae

Postby dobe12 » Fri 19 Feb, 2021 16:27


I have really bad black algae pool problems in late Spring. I don't want to go through the nightmare again this year. The pool looks great now.   
The algae is much less of a problem in early summer and after... But there's still some very mild green algae on the steps and in certain places on the bottom of the pool throughout the Summer.

I have a pool guy who's very reliable and does a great job except with the Spring black algae. He's been taking care of pools for 20 years. The algae has only been a problem in the last 3 years. Before that he controlled it.

He says it's because I have so many flowering vines and other plants. He uses shock treatment and says he always monitors the chemical balance and does everything he can to control it. But it usually takes about 4-5 weeks for it to go away.

My question is are there certain environments where no matter what you do black algae can't be controlled at certain times of the year? If not what should I tell the pool guy he's doing wrong?


I'm new here
I'm new here
Posts: 1
Joined: Sun 21 Feb, 2021 15:38
My Pool: 15x30

Re: Black Algae

Postby mustbepro » Fri 19 Mar, 2021 17:31

Black algae is more difficult to kill because it's a single celled organism that grows like a colony.

Do you use algaecide regularly?
Do you pets or animals swim in the pool?
Do you take the same swim suits to the beach / floats?
Pool Industry Leader
Pool Industry Leader
Posts: 1337
Joined: Tue 17 Oct, 2017 10:52
My Pool: 12 x 24 (45m3) liner pool, Triton TR60 filter with AFM glass media (Activate) and variable speed pump running 0.08HP
Location: UK

Re: Black Algae

Postby Teapot » Sat 20 Mar, 2021 06:07

Black algae is not actually algae, just another thing the pool industry gets wrong. It is a cyanobacteria and hard to kill, using chlorine dioxide has some effect but on plaster finished pools it gets right into the plaster/quartz whatever.

Return to “Pool Algae & Green Pool Water”

Who is online at the Pool Help Forum

Users browsing this forum: CommonCrawl [Bot] and 0 guests