Black algae - Damaged plaster

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.

Black algae - Damaged plaster

Postby Sarah » Sun 02 Dec, 2007 13:12

Our Plaster inground 25,000 gal pool (guess 15 yrs old), Falcon 100 GPM cartridge filter, located in Florida inlet area (high water table), has damaged walls (peeling/sandy) and black algae growth on the side walls. One year ago It was ‘cleaned’ with water pressure (upper 2/3 by partially emptying it) and metallic brush, trying to “fix” huge algae growth after Hurricane damage of 2yrs ago. Today the walls breaks like sand if we scratch it with the fingers, and the bottom has peeled areas that from time to time breaks a little piece more (however it is still plaster –no “holes”- it is as if a ‘layer’ of plaster is peeling)

We have decided to resurface it but are still putting money together…

Making the story short, two weeks ago it was white cloudy, shallow bottom tiles very-very blurry, deeper area impossible to see anything, with the following levels:
TC 2.0
FC 2.0
CC 0.0
PH 7.4
TA 110 ppm
Stabilizer 130 ppm
TDS 2500

As we were recommended, I have tried keeping it in shock level with only liquid chlorine and PH 7.2, for 2 weeks now, and I was very happy to see it getting clearer and gave me hope. Bottom of pool has no algae, easy to remove w/automatic + manual vacuum, if any. But walls are another story. I hand vacuumed only small areas of wall, as it returned green/black stuff back into the pool… I was enjoying how it was getting clearer and didn’t want to spoil it… However now is the moment of truth… I have to face reality… Does my pool have any hope as it is, in any way? (While we put money together for resurfacing it?)

We have ‘invented’ a way to ‘vacuum to waste’ (by taking out the filters and connecting a hose to the empty tank), so yesterday hand vacuumed the walls, then turned off the pump, brushed (plastic brush) the walls (it cleaned the black algae only partially) and waited today morning to turn it on again and vacuum what was deposited on the bottom,; then turned off and brushed again. I’ll vacuum again late evening whatever goes to the bottom. With this, I am also eliminating some water in order to lower the stabilizer…. Green algae comes out of the walls relatively easy; however, the black algae is stubborn (approx 1/10 of the walls have it), and as I vacuum the walls, I am vacuuming sandy material off the walls too!, I don’t mind that too much for now, but was wondering if I would be able to get rid of the black algae (I should not empty all the pool- high water table) .

1) Would somebody recommend me how to keep the pool meanwhile? (Hopefully usable). We may be resurfacing it in a couple years from now – hope sooner!.

2) What would be the best bet for resurfacing material and filter system?

Thank you for reading my post. Hope to hear from you.

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Postby mr_clean » Sun 02 Dec, 2007 17:30

you are going to want to start by draining some water & replacing to lower CYA to around 80. When CYA gets to 100 or higher it makes chlorine weaker.

Your shock level of 2 is not high enough to fight algae. You need to raise chlorine level to shock levels 24ppm & then you will need to check chlorine level 2-3 times a day adding liquide chlorine to reboost as needed.
Cleaning your cartridge filter when needed & running pump/filter 24-7 until clear.
Remember with cartridge filters when cleaning them it's a good idea to soak them in a filter cleaner which helps them last longer.
Scrubbing the black-algae spots on walls & rubbing chlorine tabs on them afterwards will help remove them.
Do you know what your CH-hardness level is?

Postby Sarah » Sun 02 Dec, 2007 19:02

Thanks for answering my post

I don’t know my CH- hardness right now, but I guess I can ask for it on Monday bringing a sample to my nearby pool store.

How can I rub the chlorine tabs to the walls of the deep area (where most of the stains are)? I guess entering the pool wouldn’t be advisable due to the high chlorine… Is there any tool for that?

What I have done with the pool is : After having the pool water green, chocked it with a thriclore product, which turned it white cloudy. I proceeded to keep a chock level with only liquid chlorine trying to clear it despite of the high stabilizer. For the last 2 weeks, I have been checking it 2 or 3 times a day frequently cleaning the filters as presure increased, and are keeping the chlorine way over 10 in the attempt to see if my pool ‘resurrects’. My ‘tester’ (aqua chem. 6-way strips) is limited to showing up to 10ppm, however my pool store told me that it was in 30 last Wednesday. What I am doing is when I see that the FC purple color of the strip is getting close to 10, I add 1 to 2.5 gal of liquid chlorine, and keep checking the PH. This has helped to turn it nicely clearer (but still somewhat cloudy) while I wasn’t able to lower the Stabilizer.

The problem I have found is with the walls (I was successful cleaning the bottom but not the walls). They seem not to notice the existence of the chlorine and keep getting green and black (especially black). And I don’t know how the ‘breaking like sand’ of the wall affects the chemical reaction of the chlorine u others…

I found a way to vacuum to waste and have started yesterday evening by brushing the walls, waiting for it to sit and then vacuum. Are thinking of doing it until tomorrow (unless you have another suggestion), when it will be 1/4 empty (cannot lower it much because of the underground water of the area). The problem is that the walls are getting somewhat better but still tend to get lightly greenish until I vacuum them again despite the amounts of chlorine... and the worst part is that it is still black stained. Each time I brush the black areas, small areas of the wall cleans, the rest stays black, the surrounding water gets heavy darkened and gradually dissolves into the water, and small ‘black pieces’ as well as sandy white grains of the wall go to the bottom which I vacuum to waste later.
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Postby mr_clean » Sun 02 Dec, 2007 22:49

Vacuuming to waste the way you have done is fine but you still need to clean cartridge filter when pressure rises on gauge. Cartridge filters can catch the algae but with no backwash cleaning is needed. Sometimes depending on size of filter once a day.

I still suggest draining some water & refilling until CYA level lowers to 80 so chlorine will be more effective. A chlorine reading of 10 still is not high enough to clearup algae, get to 24ppm.
The best thing you can do is to invest in a good test kit like a Taylor K-2006 test kit from Taylorhere or from Leslie's
You then will be able to do all testing yourself.

You can buy a clamp that clips onto the end of your pole & holds chlorine tab so you can rub it on black spots.

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