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Should I Shut off the Pool to Let Dead Algae Settle?

By Tony Guerra ; Updated September 21, 2017
Dead algae should be allowed to settle to the bottom of a pool by shutting off the pool's filter.

The appearance of swimming pool algae can strike fear in a pool owner's heart. Swimming pool algae can turn clean pools into real messes in no time at all, sadly. Fortunately, treatments that can rid a pool of algae contamination exist, with the only question left being how to eliminate the dead algae. Part of the solution to dead pool algae is to shut off any filtration and let them settle out, but other actions should be taken as well.

Algae Issues

In most cases, a swimming pool algae contamination is dealt with by shocking the contaminated pool. Shocking a pool to kill off an algae contamination, though, won't clear away the dead algae left. Dead algae in a pool are so microscopically small that most will float in the water, clouding it up as fine particulate matter. Algae in general are also so tiny that not all may be trapped by a swimming pool's filter once they've been destroyed.

Settling Algae

In a swimming pool, dead algae need to be heavy enough to settle to the bottom of the pool to allow for vacuuming. Making dead swimming pool algae heavy enough to settle to a pool's bottom is accomplished through pool clarifiers. A good swimming pool clarifier will force dead algae to clump together, giving them enough weight to allow for settling. You'll rarely find that dead algae in a pool will settle to a pool's bottom without first being treated with a clarifier.

Adding Clarifiers

Once you add clarifier to a swimming pool, run the pool's filter two hours before shutting it off. Running the filter after adding clarifier to a pool will allow clarifier to disperse fully throughout the pool. Leave the pool filter off for 12 to 24 hours to give a water clarifier time to clump up dead algae or organic matter. Once dead pool algae is clumped up and settled to the bottom of the pool, vacuuming using the pool's filter will be easier.

Pool Clarifiers

Different types of pool clarifiers can help clear swimming pool water clouded up by dead algae. All pool clarifiers, though, work on the same principle of making fine particulate matter like dead algae heavy enough and large enough to settle out. Also, pool clarifiers come in different strengths, formulations and concentrations. As little as an ounce of clarifier in 5,000 gallons of water will effectively treat a pool that's cloudy from dead algae.

Pool Filtration

Once dead swimming pool algae has settled and after it has been vacuumed up, check your pool's filter if it's a sand model. Sand pool filters can become channeled and will just recirculate water, not filter it. If the pressure in your pool's sand filter refuses to rise, there's a good chance it's channeled. Channeled pool filters can't effectively filter out any remaining dead algae. Resolve channeled sand pool filters by backwashing or replacing the old sand.


About the Author


Tony Guerra served more than 20 years in the U.S. Navy. He also spent seven years as an airline operations manager. Guerra is a former realtor, real-estate salesperson, associate broker and real-estate education instructor. He holds a master's degree in management and a bachelor's degree in interdisciplinary studies.