??Black algae maybe. Ackk!! No idea why.( Pics)

orthofish

LifeTime Supporter
Jan 21, 2009
562
Northern Middle Tn.
I noticed this in my pool this evening. If it is BA, I have no idea why. :evil: The only thing I've done in the last 2 weeks is add Borates. I got in the pool with a Scotch Brite and tried to remove it with my foot, no luck. I went down in the water with my eyes open, but I had to flay around so much to stay under, the water was too turbulent and I couldn't get a good look. It's in the shallow end, about 4 feet of water. Feels kinda rough. I hope nothing is eating at my fiberglass :shock:
My numbers this evening:
FC 6.5
TC 6.5
pH 7.4
TA 70
CH 210
CYA 80
Salt 3240 per strips
2600 per Pro Logic
Borates 40-50
My FC is a little high cause I think my DPD powder was bad and I kept getting 2-3ppm readings. Used some fresh today and it was 6.5.
I'm doing an overnight FC test tonight. Will know in the a.m. about it.
I didn't get very aggressive with the Scotch Brite cause I didn't want to damage the gelcoat.
What do y'all think????? How do I get rid of it???? Hope you can see it on these pics.
 

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JasonLion

TFP Expert
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LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
I doubt that it is black algae. Black algae almost never grows on fiberglass and when it does it can be brushed off.
 

Butterfly

TFP Expert
LifeTime Supporter
May 30, 2007
10,045
South Carolina
Your CH is low. Here's a copy from one of waterbear's posts:

The calcium is supposed to help prevent staining and to prevent cobalt leaching from the gelcoat. Cobalt staining is very common in fiberglass pools and looks like little black dots that seem to grow like a crystal. I keep mine at about 250 ppm. I used to keep it lower but I had iron stains more often. Since I increased the hardness of the water I have had much less iron staining in the pool. Didn't even need to use any ascorbic acid this year!
 

orthofish

LifeTime Supporter
Jan 21, 2009
562
Northern Middle Tn.
Thanks for the replies. I'm going to WalMart today for more Calcium. How tough is the gelcoat???? What would be a good way to get the black stuff off??? It does appear to be cobalt staining.
 

Butterfly

TFP Expert
LifeTime Supporter
May 30, 2007
10,045
South Carolina
orthofish said:
I did a search on cobalt staining and I think I've got it. Thanks Jason and Butterfly for helping me recognize what the problem is.
You're welcome and please keep us posted with your progress.

Don't forget the pics :-D
 

orthofish

LifeTime Supporter
Jan 21, 2009
562
Northern Middle Tn.
Do you think I should get my water tested for metal. My house plumbing is copper, but other than that I don't know where it could be coming from. I seem to have noticed the stains after adding the borates. The area I'm seeing the stains is where I poured in the borax and swept it around. ????
I shudder to think I would be taking water to a PS for testing :shock: I do have a copper test kit for my aquariums. I wonder if that would work??? I don't know if it would work with chlorinated water, as obviously there is none in my aquariums. :-D
 

orthofish

LifeTime Supporter
Jan 21, 2009
562
Northern Middle Tn.
Butterfly, you asked for an update. I've got my CH up to 275 at last check. Will check again this evening. I had some Vit C tablets at home. Crushed them a little and put in 2 different pieces of pantyhose. Stood on them, on the stains, and did the "twist" a little :-D Didn't see any difference in the stain :evil: How long should I have stood on the stains???
Then I checked the expiration date on the tablets and it was 2007 :oops: Could that be the reason why they didn't work? I really do hope so. I'm going to get some fresh ones this afternoon and try again. Any other suggestions?
With the color of my pool, I'm really the only one that knows there in there. But I want them gone :grrrr:
Hopefully with the CH raised it will stop their reproduction :|

edit: Not meant specifically for Butterfly. Anyone can chime if the urge hits :lol:
 

Butterfly

TFP Expert
LifeTime Supporter
May 30, 2007
10,045
South Carolina
Maybe some new Vitamin C tabs will help :) Holding the crushed tabs on the stain for thirty seconds or so should work, but maybe longer.

Yes, I think I'd have the fill water tested for metals.

Are you using well water?
 

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