Black / Brown algae

[David Kol]

We have a 24 ft above ground pool that started to have this problem of blackish patches on the bottom on the pool mid last season (3rd year for the pool). Adding chlorine seemed to help remove the blackness for a few days. We had hoped that when we opened the pool this year things would be better. This was not the case. The bottom of the pool is very dark and reminds one of the scum you see on an uncleaned sink or tub. (( nThis is the worse it has been when opened in the spring)) Vacuuming the pool easily removes the top layer (almost a soot like substance), but leaves a layer the requires somel elbow grease on the vacuum pool to loosen. The blackish patches that were there last year are still there. We have been giving a ton of advice that has failed to produce any good results. We have always thought that we took good care of the pool and feel this is not from neglect. Before we get to deep in this year, i decided to search the internet and find a forum and ask for HELP. This is where I'm at as of today. Opened the pool 2 days ago, and added water to a level that would operate the filter. Started to vacuum. This has started to clean up the bottom of the pool. Added 2, 2 -1/2 inch diameter chlorine pucks and 4 oz. of algecide last night. The filter has been on for 2 days. I've come to the conclusion that i'm not going to lick this problem alone, and could use some help.

Thanks in advance for any help.

David

[duraleigh]

Hi, David,

Ben (pooldoc) recently posted an informative thread on black algae.....it sure sounds like you've got it.

Go to advanced search and do black algae and Pooldoc as the member (on the right of the screen). Essentialy, he advocates persistence....scrubbing, clorox and maintaing your water balance. Read that post....I thought it was very good.

[David Kol]

Dave, I did the search, before the original post. I also did another and found his reply to a salt water pool situation. If you have the post info your talking about, please let me know.

Thanks

David

[David Kol]

After a couple of hours of reading posts, it was easy to figure out that there is a lot of good help available here, but I need to provide GOOD info for people to work with. Here is what I can tell you.

Total cl is 0.7 ppm
ph is 7.9
hardness is 160 ppm
alkilinity (with stabilizer correction) is 151 ppm
cya is 30 ppm
copper is 0.38 ppm
iron is 0.0 ppm
borate is 80.00
nitrate is 5.00

Again, since opening the pool 3 days ago I have added 2, 3" cholrine pucks and approx 4 oz. of algecide to the pool. I have vacuumed a couple of times, cleaned the filter ( cartridge) once and let the filter run 22 hours a day.

The above information was obtained by taking a sample to a pool store. Denise obtained a print out of the results and called me with them. I beleive I got them correct, as we had a semi bad connection.

We are trying to correct a blackish patchy situation on the bottom of the pool. I can try and take pictures tomorrow that might show the problem. Scrubing, from the deck with the vacuum brush seems to have no effect.

Thanks in advance for any help

David / Denise

[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