Treating Black Algae

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Treating Black Algae

Black algae grows on porous pool surfaces, like concrete, plaster, and gunite. It presents itself in the form of black spots often found in corners, steps, and other hard to reach areas in your pool. It thrives in both sun and shade, making it the most aggressive form of pool algae as well as the most difficult form of algae to get rid of. Here’s what you can do to make sure black algae doesn’t take over your swimming pool again:

How to Treat

Black algae is certainly a challenge. It has deep roots that keep it firmly embedded in place and a natural protective layer that makes it difficult for chemicals to penetrate. To begin the process of ridding your pool of black algae for good, start by scrubbing your pool with a nylon brush. You will need something tough to help get past the protective layer. If it seems as if the black spots are gone, there may still be roots beneath the surface, so the next step is to use chlorine tablets. Break a tablet in half and rub it directly onto the affected surfaces. This helps kill the roots. 

Next, clean your filter. Black algae flourishes when the water isn’t at its best. You will then need to shock your pool with granular chlorine. Use three times the amount you would usually use, about three pounds per 10,000 gallons of water. Do this in the evening and run your pool filter for at least 24 hours after adding the shock treatment. Wait a few days, then do a follow-up shock treatment, using one pound per 10,000 gallons this time. Shock your pool as needed until the black algae has gone away. 

Keep It Away

To keep black algae from coming back for good, keep up a regular maintenance routine. Test your water regularly, checking alkalinity, pH, and chlorine levels. Brush and vacuum your pool and run the pump regularly. Shock the pool once a week and clean any pool accessories.

Although black algae won’t hurt you or cause you to get sick from swimming in a pool where black algae is present, it can encourage bacteria development, which can be unhealthy. Following these tips will help get rid of black algae as soon as you spot it.

Rising Sun Pools & Spas

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