Think I have black algae??

setsailsoon

LifeTime Supporter
TFP Guide
Oct 25, 2015
1,453
Stuart/FL
Really hard to say... honestly brushing doesn’t touch it so for weeks I’ve just assumed it was stained plaster... but then someone on a local Facebook group had something similar but worse and everyone was saying black algae... it doesn’t “look”like algae to me as far as what I’m used to mold looking like..

To test I took a pvc pipe and put it over a spot and poured acid in and let it sit for like 20 seconds and it went away... didn’t work on a second spot... obviously this approach won’t work on some of the angles and stuff plus I don’t wanna put too much acid in.

So thanks for the help guys... would you think just getting a couple gallons of chlorine and dumping them in is the right move here, opposed to just setting the generator high and waiting? Not sure how fast it reacts to setting changes.
If you brush vigorously and it doesn't go away it's something else. I've used the trichlor tablet scrub very effectively for stubborn algae. Careful with the acid approach, you can eat up a lot of plaster very quickly. In case you can't get it off with black algae treatments we'll get a stain expert to weigh in. @Swampwoman .

Chris
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,646
Northern NJ
At the black algae recommended FC level between target and SLAM the pool is safe to swim. Nothing in the article should mess up the birthday party.
 

JamesW

TFP Expert
Mar 2, 2011
16,323
I'm not seeing black algae. Black algae is similar to black mold. It's soft and spongy. You can scrape black algae off and it's a bluish green moldy type substance.

It looks more like maybe copper stains.

Try putting ascorbic acid (vitamin C) on it.

Do you have copper in the water?

Have you used calcium hypochlorite recently?

Note: Your signature says that your pump is a superfood?
 
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Rich G

Active member
Apr 7, 2018
38
WPB, FL
I'm not seeing black algae. Black algae is similar to black mold. It's soft and spongy. You can scrape black algae off and it's a bluish green moldy type substance.

It looks more like maybe copper stains.

Try putting ascorbic acid (vitamin C) on it.

Do you have copper in the water?

Have you used calcium hypochlorite recently?

Note: Your signature says that your pump is a superfood?
That’s pretty funny... never realized it said superfood, it should say superflo.

Not sure if i have copper in the water, my test kit doesn’t test for that... I could potentially take my camera in the pool and get a much closer picture. I have not used calcium hypochlorite.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,646
Northern NJ
Article says:

gently scrape a sample of the suspected black algae with your fingernail and then smudge it on plain white paper. If the smudge scrapes off and is a greenish color, then it’s black algae

Have you done that?
 

setsailsoon

LifeTime Supporter
TFP Guide
Oct 25, 2015
1,453
Stuart/FL
I agree with James, the black algae I've encountered is very black and usually in spots not even coverage like you have. When you brush or scrape it turns green and comes off in a green clump. Try a vitamin c as James suggests.

Have you ever added anything that has copper?

Chris
 

mguzzy

Well-known member
Jul 8, 2015
701
OV, CA
Did you by any chance use some of that Clorox pool salt? It has metal contaminates in it. If you don't have a test kit for metals .. the dreaded pool store will test for that, at least to give you a quick ballpark.
I agree with the others.. if its not readily brushing off it is probably staining.
 

Rich G

Active member
Apr 7, 2018
38
WPB, FL
Did you by any chance use some of that Clorox pool salt? It has metal contaminates in it. If you don't have a test kit for metals .. the dreaded pool store will test for that, at least to give you a quick ballpark.
I agree with the others.. if its not readily brushing off it is probably staining.
I’ve used the Clorox stabilizer several times but not Clorox brand pool salt.. I took a stainless brush to it and scrubbed hard and it did nothing to the stains