Abnormal Pool Water Algae

by Kim Bunch
(Monroe, NC )

Beginning last season, and now again this season, we continue to fight what we think is an abnormal pool water algae problem. It's large blobs on the floor, a dark color, that no matter how much we sweep, vacuum, backwash, shock, keep the cholrinator running high, it won't go away.

The water is CRYSTAL CLEAR, always. We've algae bombed, ect. Whatever it is it's staining the floor of the pool . It always seems to go back to the same spots. They are probably quarter, half dollar size, but not exactly round. HELP!!!! I've gone to my local pool store, and it's try this try that, we've spent hundreds.

Thanks for your question Kim

With your abnormal pool water algae it sounds like you've done all you can with this issue. To get a good shock you can go here:

Pool Shock

And how to clear up an algae issue go here:

Remove Swimming Pool Algae

Get a FAS-DPD Reagent K-2005 or 2006 test kit.

Water Testing Kit

If the spots are black and round it sounds to me like you may have a Black Algae issue. This kind of algae is probably the worst and normally can be found in plaster pools, although to a much lesser extent, with vinyl pools.

Black Algae

Unlike brown algae or green algae, black algae forms layers and each layer forms a scab. Even when you have good pool water chemistry it still might not be enough. You can go to the above link to get all the information you need on how to get rid of Black Algae but I will tell you now it's not fun or pretty. If it is Black Algae you're going to need to brush the spots with a wire brush to loosen it up.

Your 2nd option is to drain the pool, use the wire brush, then a chlorine tablet and really grind in the chlorine to kill the algae. If you feel this is a bit out of your expertise range you can hire a qualified pool tech that knows about and has removed Black algae before. This should help with your abnormal pool water algae.


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Jan 13, 2015
Didn't Winterize My Pool, Now It's Still Green
by: Walter

FYI...I did nothing to the pool over the winter. Didn't put in any chemicals and did not cover it so I know it was going be hard to get back. Can you help. AND I HAVE LEARNED MY LESSON ON WINTERIZING. NEVER AGAIN WILL I NOT DO IT.

My pool chemical's are perfect, but my pool is still green. Can u give me a clue of what to do?

Thanks for the question Walter

I have answered many questions concerning this very issue. Here a some links that can help you:

Algae Will Not Die In My Pool

The above link tells exactly what you need to do.

Pool Opened By A Company On Monday -- It's Still Green Water On Thursday!

Swimming Pool Algae

Green Pool Water

Green Swimming Pool Water In Above Ground Pool..Algae..Shock

Clearing up a green pool is basically the same procedure. It's shock, brush, vacuum, keep filtering and backwashing. There are step-by-step guides in the above links and the chlorine charts you need for a proper shock.

Swimming Pool Chlorine

Also check out the pool Q&A forum.

Swimming Pool Questions and Answers

Hope this helps and have a fun and safe swimming season.


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