Hi everyone,
I’ve got a saltwater pool, and I just noticed some stubborn black spots on the walls that I think might be black algae(See photo for reference). Has anyone dealt with this before? What’s the best way to treat it? Any advice would be greatly appreciated! Thanks!
It resembles fertilizer. Are the spots elevated, or do they feel similar to the rest of the surface?
@BreaststrokeBuff Definitely not fertilizer. It’s green algae. Burnt fertilizer would resemble a comet and have a rusty color.
That’s not black but green algae. Increase the chlorine or lightly sprinkle some trichlor over the area, or rub a tablet on the spots.
Whether it’s black algae or something else, it’s ugly, unhygienic, and has to be dealt with. Even if your chemical balance is spot on, a SLAM might not be enough to fix the problem by itself.
Try this: grab a chlorine puck, put on a latex glove, and scrub the puck directly on the algae until it turns white.
I had to do this last week, and within 24 hours, the algae was visibly gone. It might still be dormant, I’m not sure, but so far, it hasn’t returned.
I occasionally grab a chlorine puck and my goggles, then swim around targeting areas like this. It’s tough to completely eliminate.
While it’s dark, it’s not black algae.
Black algae is like the devil’s herpes for pools—once you get it, it never really goes away. It embeds itself deep into the plaster. You might be able to keep it under control with high chlorine levels and metal-based algaecide, but you’ll never completely eliminate it. Let the water get unbalanced for a few days, and it’ll come right back.
Speaking from experience—I bought a house with it 15 years ago and have been battling it ever since. Next year, I’m planning to replaster to finally get rid of it for good.