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Black Algae Woes: How to Get Rid of It Permanently

Learn about what causes black algae and how you can eliminate it from your pool.

There are few things that will make a pool owner shudder in fear more than black algae. This fungus has an uncanny knack for hiding away in the cracks and crevices of your pool liner and decking, only to resurface about the time you think you've finally got it licked. While black algae are a more challenging problem than other types of algae, there are solutions to the problem. We will tell you how to use potent products and plenty of persistence to get rid of that unsightly fungus for good.

The Curse of Black Algae

Black algae are characterized by black spots that appear on the sides of the pool. Black algae form deep roots into your pools structure, making it difficult to get rid of it completely. You may think the problem is gone because you no longer see the spots, but they will reform eventually, using those deep roots to grow back again. It also forms a waxy outer layer that protects it from the chemicals placed in the pool to eradicate it. You will need to attack black algae from many angles if you want to be sure this stubborn fungus is gone for good.

Steps for Elimination

First, run a test on your pool water to check chemical levels. Algae grow when conditions are prime, which usually means the pool water is lacking chemicals that typically keep growth at bay. Once you know your numbers, add the necessary chemicals to bring your water back to an optimal balance. You can then scrub down the walls of your pool using a stiff brush, to loosen algae and make it easier for the chemicals to do their job.

Many pool owners spot treat black algae using chlorine tablets before adding treatment chemicals to the pool. However, if you have a pool liner that would be sensitive to such treatment, forgo this step. Next, use a concentrated amount of a copper-based algaecide to treat the spots directly. Leave the algaecide on overnight to allow it plenty of time to work. The next day, scrub the remaining algae spots and vacuum the pool. Re-check chemical levels and add a shock treatment to the pool. You may need to repeat the algaecide and shock treatment as a preventative measure.

In extreme cases, black algae may need to be treated by a professional pool service. In these cases, the water is often drained from the pool and a chlorine bath is performed. This involves covering the entire surface of the pool with chlorine spray to kill off any elusive spores so the algae does not return. If algae cannot be removed through this method, the affected portion of the pool may need to be removed and re-plastered.

Black algae are a stubborn microorganism to get rid of, but early, aggressive treatment will often do the trick. Begin these steps as soon as those black spots begin to appear and you should be able to enjoy your algae-free pool for the rest of the swimming season.