Black / Brown algae

[duraleigh]

Hi, David,

Yeah, it's the one about salt pools. I'm gonna' copy it here, just to make sure we're on the same page. I can't help...I've never experienced it. I thought Ben's info was very informative, however.

As far as brushing . . . it's important, but persistence is more important than strength. I've seen folks attack it, as if one really, really hard scrubbing would get it all cleaned up. No such luck! If you want to get rid of black algae after it's become established, you have to commit to approaching it as a long term problem. Think weeks, not days.

(Of course, many pool stores will be happy to sell you any number of products that promise quick results. And, they'll also be happy to explain -- when you don't get quick results -- why it didn't work for *you*)

What's important is brushing enough to remove any dead top layer, or at least to scratch it, and expose the live algae to the chemicals in the pool. But it's much more important to brush some today, and the day after and the day after that, than to brush really, really hard today.

Another thing you need to keep in mind: black algae doesn't grow rapidly, and didn't appear in your pool suddenly. It's there because, day after day, the chemical levels weren't right. And, once it's gotten a start, it's unlikely you will EVER get rid of all the roots and spores penetrating into your pool. (I'm assuming it's NOT a vinyl or FG pool??) So, even if you 'get rid of it' for now, it will come right back unless you learn to maintain proper chemistry day after day in the future.

Now, you didn't post test results, or tell how you've been treating your pool, so I don't really know what you've done wrong. There are numerous possibilities; here are a few of the more common:

• Low, or inconsistent, chlorination.
• High pH, not compensated for with higher chlorine.
• High stabilizer, not compensated for with higher chlorine.
• Poor circulation, or not running the pumps enough.
• Porous or damaged plaster, not compensated for with higher chlorine.

Keep in mind that a single day -- or even week -- of one of these problems wouldn't lead to black algae. It just doesn't grow that fast.

So, what you really need to first, is figure out what's been going wrong, and learn how to correct that. Otherwise, anything you do to get rid of the algae will be only very temporary in effect! Fortunately, as many PoolForum members can tell you, doing it right is easier and cheaper than doing it wrong, once you learn how!

Meanwhile, except for the trip and fall hazard from the black algae, there's no reason to not use the pool while you work on the problem . . . as long as you have chemistry that's adequate for sanitation

Once you figure out what you need to correct, and take care of that, the solution is pretty straight forward:

• Brush regularly.
• Maintain chlorine levels 50% higher than you'd otherwise need to maintain.

Using polyquat will help some, especially if you can FREQUENTLY brush hard. But, it's still going to take weeks, as a rule, not days.

Best wishes,

Ben
"PoolDoc"

[David Kol]

From what I've read so far, it looks like I need to get the chlorine up first and then lower the ph a little. I've added two gallons of 5.25% bleach to the pool tonight. Will test in the morning before I have to go out. Based on the readings posted above, I don't think two gallons will get the job done. The more I get to read the less sure I am of what my problem is ( the dark patches on the bottom). I hope to be able to take and post a few pictures.

David

[duraleigh]

David,

Did you get my PM re: your test results?

[David Kol]

Yes on the PM. Test results are above. Total chlorine was up to approx 1.5 PPM this morning. I added two more gallons of 5.25% bleach. Will check when I get home this afternoon.

David

[CarlD]

David:

You are going to need to be far more aggressive to get your algae under control.

1) You need to get your pH down to the lower 7's--chlorine will be more effective. You can use muriatic acid or dry acid, but the muriatic will be faster.
2) 2 gallons of bleach won't be nearly enough. You need to get your FC level up to 15ppm and plan on keeping it there for up to several weeks. You'll need to check your FC level 2 to 3x per day and add bleach as needed. Use MWSmith2's bleach calculator...do a search for it and download it, it's free. Plan on adding lots and lots of bleach over the next few weeks. You can also get liquid chlorine in 5 gallon "carboys" from pool stores. It's usually 12% (exactly twice as much chlorine per gallon as ultra bleach) and you can add a lot of chlorine with it faster and easier and with less waste. But it's usually more expensive than bleach--plus you give a deposit on the carboy. But if it's $12 for the carboy, that's a very good price. Anything under $15 is probably OK.
Remember Liquid Chlorine, liquid shock and bleach are all the same thing--just different concentrations. Regular bleach: 5.25% Ultra/liquid chlorine 6%. Carboys and liquid shock: 12%. PS: Make sure the carboys are recent deliveries because 12% breaks down rapidly to 6%--plan on using it quickly.
3) Brush your pool everyday--you don't have to scrub it and kill yourself and maybe tear your liner, the object is to loosen and open up the algae there to the chlorine.
4) You want to vacuum to waste everyday.
5) Do not use trichlor pucks, or dichlor powder. Your CYA is 30--that's good enough for now. If you want it higher, you can raise it later...Remember, when you are up to your...backbumpers....in alligators it's not the time to think about the objective of draining the swamp....
6) What you need to do is very simple, but not easy. It's not complicated, but it is hard work. You need to be persistant, decisive and patient.

[David Kol]

Hard work is still cheaper then the other option. (( at least when you let the dog in, he quits barking)) <G>. I should be home in an hour an will add bleach / chlorine to get the level up to 15ppm.

Again, thanks to all

\David

[David Kol]

Here are 2 pictures of the problem. These patches are more towards the outer edge of the pool. 24 ft pool, and the problem is fairly well confined to the outer 6 or 7 feet. Approx 6 to 7 feet from the center out has no noticeable problem (yet) As the cl level is increased, the darkness of the patches starts to go away.
I am now working on getting the cl to the range of 15ppm (as suggested here). Should I work on lowering the PH from the 7.9 now, or what until I get the CL level up.

Thanks

David

[gregugadawg]

black algae isn't going to grow in a vinyl lined pool, it needs a rough surface to attach on to as in a plaster surface. Also black algae is going to be no larger than a quarter in diameter. It is possible to be brown/mustard however that easily brushes up but is persistent. Try to rub a vitamin c tablet on the discoloration and see if it comes up, if so then it is a stain.