Black Algae Above Waterline


New member
Aug 22, 2020
I have a 10,000 gallon fiberglass, salt water pool with tile at the waterline. I don’t have any issues in the pool, just stubborn algae in the silicone that holds the tiles. I’ve tried scrapping is with a razor, spraying chlorine, chlorine tablets. Nothing works. In the first couple years I had my pool I kept the cover on a lot not understanding that I should not have been doing that and I think this is when the problem started. What can I do?! I am losing my mind. Shocking doesn’t help because the water isn’t that high.


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Mod Squad
Gold Supporter
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
I would suggest spraying with a 50:50 water:liquid chlorine solution and a firm brush. If that is truly black algae it has roots that go into the grout and they need to be disrupted.

Maddie :flower:
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