The Basics of Pool Algae.

All About Algae

In Arizona Swimming Pool Blog by Les Greenfield, Owner / Operator

All About Algae

One day your pool is clear and clean, and the next, there’s that tell-tale green tinge to it, congregating first in a small area before it begins to spread. Algae: the natural enemy of pool owners around the world. As Sun Tzu says in The Art of War, “In order to beat your enemy, you must first know your enemy.” Here’s everything you need to know about algae.

What are algae?

Algae refer to a diverse class of living aquatic organisms that first appeared 1.6 billion years ago. Algae may be single-celled or multi-celled, and appear in recognizable forms such as kelp and seaweed, or in symbiotic relationships with coral reefs and lichen. Like other plants, they take in carbon dioxide and expend oxygen as a byproduct. Recent studies estimate that there are 72,500 algal species on our planet, both on land, in the sea, and in transitional areas in between.

Algae play a major role in natural marine habitats as a base energy source in the food chain. We also eat seaweed and kelp for the health benefits they provide. Algae are used in energy production, as a fertilizer, and have been introduced to urban sewage and rural agricultural drainage systems to cleanse and improve water flow. Algae scrubbers are used to balance water levels in hobby aquariums. Marine biologists use algae to determine biological factors and chemical levels in water. In this respect, the algae you find in your pool may provide with you crucial information about your pool water.

Algae in pools.

Algae begin to grow in pools when there is a pH imbalance in the pool water. Algae enter outdoor pools from different weather conditions such as wind and rain. In some cases, they may travel to your pool on a swimmer’s trunks or bathing suit, carried from a different marine environment, such as a pool or the ocean. Algae also thrive on other plant life that enters the pool, such as leaves or mown grass. Though algae do not pose health risks to swimmers, they create conditions for other bacteria to thrive. As algae grow in pools, they can cloud the water and transform it into an unappealing, murky color that will dissuade swimmers.

The different colors of algae will indicate to you the imbalances found in the pool water:


  • Green algae. Green algae are the most common variety found in pools, usually floating on the surface of the water or clingingly lightly to walls, and are the easiest to eradicate. They indicate a problem with the pool’s filtration and sanitation systems. Make sure your pool filters are emptied and cleaned regularly.


  • Yellow algae. Yellow algae usually occur in shady areas of the pool and are more difficult to remove. You will need to increase the level of chlorine in your pool to eradicate yellow algae, following instructions provided by your pool specialist.


  • Black algae. Black algae are the most difficult to eradicate in pools, as they have the tendency to grow into the grout, concrete and tiles of the pool structure. If a pool has been overtaken with black algae, you will want to contact a professional pool cleaner.

Algae are an important part of the greater biosphere, but they are unwelcome in swimming pools. Prevent algae growth in your pool by maintaining your pool’s cleanliness by brushing pool surfaces and regularly cleaning your filtration systems. For more powerful solutions, speak to a pool specialist to learn more about chemical options that prevent and kill algae.

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