It can become a food source for harmful bacteria that cause health problems, stain and damage pool walls, and it can clog filters and other parts of pool sanitation systems. Algae can also cause surfaces around the pool to become slippery, creating a slip and fall hazard. Algicides, in combination with chlorination and other water maintenance practices, help prevent these serious (and costly) problems.

How are algicides applied to pools/spas? The best time to apply an algaecide is 24 hours after a shock treatment. (Note: do not apply shock treatments and algicides simultaneously as the algaecide will render the shock treatment useless.) If the algae is growing on the sides of the pool, first scrub it down with a brush. Next, with the pump running (and while wearing proper personal protective equipment), the product is then measured and applied at several points throughout the pool to ensure equal distribution. Twenty-four hours after the application, the pool should be vacuumed to remove the dead algae. The process can be repeated until the water is clear.

Are algicides safe? Like all biocides, algaecides are regulated by the federal government (specifically the Environmental Protection Agency or the Food & Drug Administration), so it’s important to make sure any products you use are federally-approved. Moreover, you should carefully read and observe the measurement and usage guidelines (which usually advise against swimming in a pool for 30 minutes after it has been treated).