Black Algae Help

Txpoolgal17

New member
Aug 25, 2021
3
Midland, TX
Pool Size
28000
Surface
Plaster
Chlorine
Liquid Chlorine
New-ish pool owner here and having trouble getting rid of black algae. (Or so I think it’s black algae).

I’ve followed the steps of getting my pH down, super chlorinating, and then scrubbing the spots with a wire brush, but they keep coming back or don’t disappear entirely. I use a Taylor water chemistry kit and my water levels are as follows - pH 7.8 (usually on the higher side but I add MA a lot), TA - 110, CH - 450, CYA - 30, temp - 83 degrees. I normally keep chlorine between 2-3 ppm using bleach, but I get up to 10-15 and leave it when I am trying to kill the algae. The algae has been in the pool for months now.

The pool and plaster is 16 years old, and I’m lost on what to do next.

Also, Is it actually safe to swim with small amounts? (Spoiler - we have all summer and are still alive). Thanks y’all!
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,434
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Welcome to the forum!
Have your read Black Algae - Trouble Free Pool
Also, a CYA of 30 in Midland I would think would be difficult to keep your FC from dropping below minimum. You say you keep the FC at 2-3 ppm, but your consumption each day would be 3-4 ppm, so be sure to follow the FC/CYA Chart
It is safe to swim in the pool as long as your FC is above minimum for the CYA.
Black Algae is cyanobacteria. So not actually algae.
I suggest you read ABC's of Pool Water Chemistry.
 

Txpoolgal17

New member
Aug 25, 2021
3
Midland, TX
Pool Size
28000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks for the reply! I will definitely read your links. I add bleach every evening and test every couple days, so I think my FC is staying in the range. We had battled high CYA (120+) when we first bought the house and got the pool, so I have been very careful about not getting to the same point as before. I didn’t consider that maybe 30 is too low.
 

Katodude

Silver Supporter
Aug 22, 2017
1,718
West Palm Beach/Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
So here is my trick. Get a mask and snorkel and a bamboo bbq skewer. I pick at the spots. Or use a small wire brush to do the same. Then I put LC in a pump sprayer and hit the spots that you picked at or brush with a high dose.

Repeat the next day.

Then keep your FC elevated as Marty suggests and you should be fine.
 
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