12" diameter black algae stains

RANDY M

Silver Supporter
Jul 19, 2010
31
Santa Clarita, CA
I'm new here and hopefully my picture is attached. The stains have been there for years. The stain on top of picture with white circle is where chlorine tab was. The stain on bottom of picture is where I used dry acid in a sock. Can black algae get this big? Thanks.
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,177
SWSuburban Chicago, IL
Hi Randy, very, very odd stains...
In the stain at the bottom of the pic, it looks like some fading of the stain has taken place - you are saying you held dry acid in a sock there?
I can't tell the area you are referring to when you discuss a chlorine tablet? I see three other large black circles...
 
G

Guest

Yes, it appears to be black algae. I have seen it get that big before.
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,177
SWSuburban Chicago, IL
Well, then yeah, I'd concur with Bruce that it's the dreaded BA. Is it anywhere other than these 4 circles? If not, I'd spot treat with chlorine tablets.

If the BA is living, you need to brush with a SS brush to knock the heads off so the chlorine can attack the insides. BA has a chlorine resistant outer shell - brushing is the key here.
 

RANDY M

Silver Supporter
Jul 19, 2010
31
Santa Clarita, CA
I've added 2 close-up pictures to hopefully verify its black algae. Also went to pool store for water test.
FC-5+
TA-200
CYA-100+
Ph-7.8
CH-500+
30,000 gal.

I added qt of acid and 30 oz genesis shock since test.
Cruised the site here and realized I'm makings things worse. I've turned off the auto feeder of tablets. Until I get a chance to do a partial drain should I add liquid chlorine or bleach if this is algae?
Debating on buying FAS-DPD today or ordering TF100 and waiting for delivery. Located in Southern California.

Please advise on anything and everything. Thanks
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Your first step is to get CYA down to something reasonable, I would aim for CYA around 40 to 50. That means either a lot of water replacement or an RO treatment.
 
G

Guest

How far south in Southern California are you? If you are close by, I would be happy to come and look at it for you. You can PM me if you don't want your location public!
 

taekwondodo

LifeTime Supporter
Apr 26, 2009
419
You know to me, that looks like an organic stain - like someone had a pile of leaves or, as in the last pool I cleared, immature dates by the 1000s or something that's just sat there. Regardless, like everyone else says, get your CYA down, then your CL up. I find that both organic stains and black algae will fade rather quickly if you maintain FC about 2-3 x MinFC level for several days in a row.
 

RANDY M

Silver Supporter
Jul 19, 2010
31
Santa Clarita, CA
I have drained half my pool and refilling now. Ordered test kit, should be here next week. Tried to scrape or smear the spots. Nothing. Tried vitamin c tablet. No change. Rubbed 3" puck on it; maybe dulled it a little. Ordered test kit, should be here next week. Then I'm sure I'll have more questions. Thanks everyone for all your help.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
One trick that often works on black algae on the bottom of the pool is to get some powdered trichlor, brush vigorously with a stainless steel brush and then put a layer of trichlor powder directly on the black algae. If you do this too much it can damage the pool surface, but if done correctly and with a little luck it can take care of things in one application. If you do try this, treat a small area first and see how it goes before tackling the rest of the spots.
 

RANDY M

Silver Supporter
Jul 19, 2010
31
Santa Clarita, CA
I received my new test kit. Even after draining about half the pool;
FC-14
CC-0
TC-14
pH-7.5
T/A-240
CH-860
CYA-100+
Tested CH assuming copper in water from black algae killer 2 weeks ago(which didn't even touch it)
I'm assuming I'll have to drain half the pool again? (After my water bill cycles a month)
Any help is appreciated. Thanks
 

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