Seeking advice on beating back the dreaded black algae!

[ebcinmv]

First, thanks to you oh wise pool mavens for the answers to a dozen questions that helped me already this year!
With your help, I’ve got my SWG working properly (had to clean the scale off the cell) and believe I have got the pool clear and balanced. The water is very clear as you can see the drain which is 9 feet down. This is the first time we have started the year with clear water. In the past, my husband used pucks, bad pool store advice, and tons of random chemicals, and we had sky high CYA and CH and often a dark green pool. We used reverse osmosis to clean the water, installed an SWG, and I have been religiously following TFP methods ever since.

But I would love to get your advice on what can be done to get rid of some black algae.

The stats per my K-2006C test kit are:
pH = 76
TA = 110
Cl = 26
CH = 230
CYA = 35
The chlorine is high right now because I cranked the SWG up to try to beat back what seems to be black algae (diagnosed per instructions on TFP). I believe we got the algae because of suboptimal chlorine last year when we were getting the SWG going (kept having to add salt). And I didn’t realize Cl should be higher is a SW pool. The high chlorine has indeed made a big dent as much of the algae went from black to a very pale gray. We can’t scrub the deep end very well, and I know that is recommended.

Is there anything else we can do to beat back the black algae?

 

[Bperry]

First, thanks to you oh wise pool mavens for the answers to a dozen questions that helped me already this year!
With your help, I’ve got my SWG working properly (had to clean the scale off the cell) and believe I have got the pool clear and balanced. The water is very clear as you can see the drain which is 9 feet down. This is the first time we have started the year with clear water. In the past, my husband used pucks, bad pool store advice, and tons of random chemicals, and we had sky high CYA and CH and often a dark green pool. We used reverse osmosis to clean the water, installed an SWG, and I have been religiously following TFP methods ever since.

But I would love to get your advice on what can be done to get rid of some black algae.

The stats per my K-2006C test kit are:
pH = 76
TA = 110
Cl = 26
CH = 230
CYA = 35
The chlorine is high right now because I cranked the SWG up to try to beat back what seems to be black algae (diagnosed per instructions on TFP). I believe we got the algae because of suboptimal chlorine last year when we were getting the SWG going (kept having to add salt). And I didn’t realize Cl should be higher is a SW pool. The high chlorine has indeed made a big dent as much of the algae went from black to a very pale gray. We can’t scrub the deep end very well, and I know that is recommended.

Is there anything else we can do to beat back the black algae?

You should be following the SLAM process. CYA results are measured in 10’s and anything inbetween decades is rounded up. So your CYA is 40ppm.

That means your FC SLAM level is 16ppm. If your water has 26ppm FC then you are risking damage to equipment and surfaces.

Heres a link to the SLAM process:

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

 

[ebcinmv]

I was aware of the SLAM procedure, just wasn't sure if that was what was needed at this point.

A month ago, the chlorine level was zero and the SWG wasn't working due to cold water and scaling and possibly low salt. There was a light amount of typical green algae. I used liquid chlorine to bring the Cl level up to the desired level while it was cold. I cleaned the salt cell, brought the salt level up, and nature warmed the water. I then adjusted pH and CYA. The liquid chlorine seemed to take care of green algae, but the black algae remained. I set the SWG high in hopes of killing off the black algae and I scrubbed the parts I could reach.

Given that the Cl level gradually rose and kept climbing up to 26 (!) over a couple of weeks, doesn't it seem as if the SLAM has effectively been done? Could I do the Overnight Chlorine Loss Test and the 0.5 CC test and see if the pool passes those?

 

[ajw22]

If you truly have black algae the SLAM process alone will not clear it. It takes picking the black algae embedded in the plaster. And direct application to the surfaces of chlorine.

@Katodude has written about how he has conquered black algae.

 

[Bperry]

I was aware of the SLAM procedure, just wasn't sure if that was what was needed at this point.

A month ago, the chlorine level was zero and the SWG wasn't working due to cold water and scaling and possibly low salt. There was a light amount of typical green algae. I used liquid chlorine to bring the Cl level up to the desired level while it was cold. I cleaned the salt cell, brought the salt level up, and nature warmed the water. I then adjusted pH and CYA. The liquid chlorine seemed to take care of green algae, but the black algae remained. I set the SWG high in hopes of killing off the black algae and I scrubbed the parts I could reach.

Given that the Cl level gradually rose and kept climbing up to 26 (!) over a couple of weeks, doesn't it seem as if the SLAM has effectively been done? Could I do the Overnight Chlorine Loss Test and the 0.5 CC test and see if the pool passes those?

You would fail one of the three SLAM passing criteria which is “no visible algae dead or alive”.

Your gonna have to brush it or pick at it like deacribed above.

 

[ajw22]

Black algae

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Search results for query: Black algae

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[Katodude]

The posts that @ajw22 listed pretty much describe the methodology.

Pick at the the black algae spots with some sort of physical method. Wooden stick, wire brush, or my person favorite, weak pressure washer. Then apply the strongest LC to those spots. Pump sprayer, dump jug over the spot. More than once is better. Then run FC hot.

Thats pretty much it.

 

[ebcinmv]

Thanks for all of these suggestions! I had read some, but not all of the posts suggested. I was traveling, but am back and can do some of these. It seems like chlorine at or above SLAM levels for many days has done all that can be done to remove this embedded algae, so I will need to attack it with the physical methods and chlorine tabs to get rid of it. I have been scrubbing on the steps where I can easily reach, and it does appear to be working. We don’t want to drain the pool now as we just had the water cleaned by RO in June and we have had tons of rain this winter, so an empty pool seems like a bad idea.

Eventually, we will have it resurfaced, but for now, I will try scrubbing where I can reach and chlorine tabs. The bottom of the pool is the hardest to reach. Too cold now to get in there with a pressure washer and 8 feet deep at some spots that will need blasting. The only thing I can think of for now is laying chlorine tabs down and moving them from one spot to another. Good thing our CYA is on the low side!

Seriously, until I can get in the pool and pressure wash, is laying down chlorine tabs on the floor worth a try? And if so, since I want to stick with the TFP method, I’m assuming I want chlorine tabs with us a little extra Crud in them as possible. Chemically, what should I be looking for?

 

[Katodude]

I am not a fan of the chlorine tab method. Too much risk for me. But it looks like you have a lot you might want to try it, but dont leave it in one spot too long.

In order for the chlorine to work physically disrupting the BA is required. Can you get an extra long wand for a pressure washer?

 

[ajw22]

The only thing I can think of for now is laying chlorine tabs down and moving them from one spot to another. Good thing our CYA is on the low side!

Placing Trichor tablets on plaster for any length of time will allow the acid to permanently stain the pool. Be very careful if you do that.

 

[ebcinmv]

OK, Katodude and ajw22, thanks for the caution about the chlorine tabs. I didn’t think of a pressure washer extension…will look for one! The area to be treated is really large and some of it very deep. Applying liquid chlorine doesn’t seem feasible, but I can apply the chlorine tablets very carefully and not leave them in one place very long. I was planning to lay 4 or 5 flat in a net at the end of a pole and move the net around. How long do you think would be enough to kill the algae, but not so long as to damage the pool?

 

[Katodude]

I just dont have any experience with tabs to treat BA. So I just dont feel right answering that question.

LC is heavier than water. If you turn off your pump pour the LC over the spots and it will drift down to the area. It’s not exact but I think still better than tabs.

 

[kimkats]

Just make sure the tablets do not say any thing about blue blu, etc. Most of the time that means it has copper or such in them.

 

[ebcinmv]

Ok, thanks! Will look for plain tablets and be very cautious with them!

Got a new powerwasher that I can attach extension wands onto. Now waiting for the wands to arrive. I’ll report in when I have given this treatment a try!

 

[ebcinmv]

The verdict is in! As the attched photos show, the prescribed treatment for black algae worked wonders.

The algae on the step had faded somewhat after a prolonged period of high chlorine. I then power washed it and rubbed the left side with a chlorine tablet. It actually looks whiter in person than it does in the picture. It will be harder to power wash the bottom of the pool and apply the chlorine, but I’m hopeful now that the algae can be beat.

My advice to future algae fighters…act as soon as you see the first signs of the problem. The quicker you act, the easier it will be to eradicate the scourge!