Black algae?

JoeyBagODonuts

Gold Supporter
Sep 29, 2020
18
Central Texas
Pool Size
17500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
We just noticed this today around the spa drain, it is black algae? Pool was filled 7/13, chemistry has been mostly good, had one green algae bloom about 10 days ago, slammed the pool and it went away in a couple of days. Added 400 lbs of salt a couple of days ago, haven't turned salt cell on yet. Cleaned the cartridge filters today for the first time and a lot of yellowish milky substance rinsed off. I think it was mostly from dust created by cool deck install 45 days ago.

Any suggestions for the black spot?

Thanks,
Joey

black algae.jpg
 

JoeyBagODonuts

Gold Supporter
Sep 29, 2020
18
Central Texas
Pool Size
17500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
We used this salt. There's a lot of reflection in the original picture above. Around the drain, it looks sort of like graphite dust. The brush moves it around easily, so hoping it's something that fell into the pool and dissolved. We just put our Dolphin robot in the spa to see if that takes care of it.


1629206558769.png
 

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
2,440
Rancho Cucamonga, CA
Pool Size
18735
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45
That salt should be good. I use it too and have seen no reported issues of contamination.

Black algae is actually wax-like mold. If you can scrape some up with your fingernail, wipe it on a white piece of paper. If it smears dark green than it's black algae. I doubt that's what you're seeing.

Try uses the steps in the article below to identify the stain:

 
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