Black Algae – What it is, Why You Have it, and How to Get Rid of it

black algae

Black algae isn’t your typical swimming pool algae, and if you have it, the sooner you tackle it, the better.

So, What is Black Algae?
Black algae is not a stain but is an algae that grows deep into the surface of concrete pools. As a matter of fact, it is the ONLY algae that grows roots into the surface of your pool It is black to purplish in color and forms a gelatinous dome over itself that protects it from chemicals. It is very chlorine resistant and must be treated aggressively. It can grow when the surface begins to deteriorate, water has poor circulation, and/or the chemistry is unbalanced for an extended time. In poor surface conditions it will continue to reappear as its roots go deep into the surface and are very difficult to fully kill. Once killed, the discoloration will disappear.

How did I get it?
As I stated above, the most common reasons are poor circulation, and deteriorating surfaces. If your pool return jets are not pointing in the same direction, you could form “dead spots” in your pool where the water rarely moves. Redirecting your jets, and/or adding an automatic pool cleaner will help the situation, but if you’ve already had black algae in your pool, there’s a good chance it will show back up if you’re not aggresive about maintaining your pool.

How do I get rid of it?
Unfortunately, the answer to this question depends on who you ask. Some would say that you will never be completely rid of black algae. We have found one of the best methods is to use a liquid silver-based algaecide, and do a ton of brushing and filter cleaning. Each pool is different, and what works in some won’t work in others, so your mileage may vary, but as a general rule, you’ll want to make sure your chemicals are properly balanced, brush the pool at least daily, and clean the filter at least daily.

This post was in response to an email we received from our website, but we figured there are a ton of pool owners who have, or will, experience black algae at some point. If you think you have black algae and have questions, or would like help getting rid of it, feel free to contact us, or ask in the comments section below.

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