How to get rid of black algae in a pool

Pool with black algae
Pool with black algae

What is black algae?

A black algae is a thread-like growth on the rough surfaces of the swimming pool. Black algae will appear as dark black slippery spots on pool surfaces (walls and floor), and also forms a protective coating.

Black algae forms a layered structure where the first layer (which chlorine may kill) protects under layers from further destruction. Black algae are similar to the black algae that is found on bathroom shower tiles and in silicone seams near the bath. This form of algae is very slow growing but very hardy. It is extremely chlorine resistant. This is why you will need to, in addition to shocking the pool, use a copper metallic algeacide.

Some other articles I have read claim that black algae is very difficult to get rid of. In my experience, this is not true even with a severe break out. The only difficult part is making sure you brush all affected areas in the pool.




The process

I mentioned brushing. Before adding any chemicals, you will need to brush the entire pool (all black algae spots) with a STEEL bristle brush. Your nylon wall brush will not work since the black algae has a protective coating that needs to be brushed off and exposed.

Once the head of the all black algae have been brushed and exposed you will shock or super-chlorinate the pool using granular chlorine (Calcium hypochloride). Make sure you raise the chlorine to at least 15ppm for 24 hours. See my other articles on shocking the pool. Be sure to add 1 quart of liquid copper metallic algaecide.

After 24 hours the black algae should be completely gone. I recommend a quart of black algae algeacide as a precaution and for regular maintenance doses. As mentioned above, copper metallic works best for treating black algae.

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