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How to Get Rid of Algae in Your Pool

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Want to know a secret? Typical sanitizer levels are no match for pool algae. On a sunny day, algae photosynthesize and multiply rapidly, growing your microscopic problem into a pool-sized one in no time. It’s easy to ignore a little cloudiness or some stubborn, dark debris by your stairs, especially when your pool is getting heavy use.

But overlook algae for just a little too long, and you’ll wind up spending a lot of time and money to get rid of it. Before that slimy nuisance grows out of control, get rid of algae in your pool with a special deep cleaning procedure. Then make sure it never comes back by using smart prevention measures.

Swimming Pool Algae Types

The exact tint of your water might not be so obvious, plus it’ll be cloudy, so it may be difficult to tell which kind of algae has take up residence in your pool.

To be sure which type of algae is in your pool—which will determine how you get rid of it—take a close look at any spots where algae is starting to grow.

Note: Pink slime is another bacteria that grows in pools, especially inside polyvinyl chloride (PVC) pipes. It’s sometimes called pink algae, but that’s a misnomer. You can get rid of pink slime in your pool, but it’ll take some hard work. You can at least rest assured that pink slime isn’t harmful to humans. We can’t say the same for your pool, though.

Before we dive in, if you want to stop your pool from turning green right now and forever, invest in our pool care video course. You’ll learn how to keep your pool chemistry in check so you never have to deal with a green pool ever again.

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How Do I Get Rid of Algae In My Pool FAST?

The best method for clearing up your water is the same for all three types of algae with just one exception.

1. Vacuum Your Pool Manually

Automatic or robotic pool cleaners aren’t well suited to cleaning algae. Ideally, you’ll manually vacuum directly to waste, bypassing your filter and preventing recirculation of your contaminated water. When you vacuum your pool manually, pay special attention to areas with algae.

2. Brush Your Pool Walls and Floor

Scrubbing the algae off your pool walls lets your sanitizer get deeper into the remaining algae. It also stirs up the sediment you’ve brushed off so it can be killed and filtered out.

Using a stiff pool brush on a pole, brush the walls and floor of your pool. Pay special attention to corners and shady areas where algae is usually worst. As you go, your water will become cloudy, obstructing your view, so get those tough spots first.

Our Top Pick
Heavy-Duty Aluminum Extra-Wide Pool Brush
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Strong and sturdy that will last for years. 20-inch extra-wide brushing that will cover large areas and finish cleaning quickly. Clean the most stubborn algae buildup quickly. The curved edges will help clean the hard corners very easy.

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3. Test and Balance the Water

Use your test strips, digital kit, or liquid kit to test your alkalinity and pH. Balancing your water chemistry now ensures your sanitizer will be effective against the algae. High pH or low alkalinity will especially inhibit pool shock.

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Digital Water Test Kit for Pools and Hot Tubs
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This digital pool and hot tub water test kit checks for Free Chlorine, Total Chlorine, Bromine, PH, Alkalinity, Calcium Hardness, and Cyanuric Acid.

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4. Shock Your Swimming Pool

More resistant types of algae require more aggressive treatment, so if the infection is heavy, you’ll need more shock.

Even if you don’t normally use chlorine shock, for this purpose, it’s best to use calcium hypochlorite shock—and lots of it. Follow the package instructions to determine the dose for your pool size, then multiply that by two, three, or four depending on which type of algae you’ve got.

Calcium Hypochlorite Shock
$72.22
Use entire contents of bag when opened. If any granules settle to the bottom of the pool use brush to disperse. Add the recommended dosage of this product during evening hours while the filter pump is running.
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Don’t use stabilized chlorine to shock your pool. You’ll end up with too much cyanuric acid, which inhibits sanitizer, and can lead you right back to algae in your pool, or other, worse problems.

Remember to shock your pool at dusk or night. If you shock during the day, the sun will eat up most of the chlorine before it has a chance to kill the algae. And put your cleaning equipment in the shallow end while you shock your pool so your tools will also be sanitized.

5. Filter Out The Pool Algae

When your shock treatment kills the algae, it’ll turn your water a cloudy blue. Run your filter continuously for a minimum of eight hours until the water clears up.

You may add pool water clarifier to speed up the process. Be sure to check whether you need to top off your water before turning on the pump.

Clorox Super Pool Water Clarifier
$9.88

Your filter can clear a cloudy pool. But your filter needs help picking up particles that are too small. A clarifier binds these particles together, so your filter can remove them easier.

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6. Test Your Pool Water Again

You may use your usual test methods or run a water sample to your local pool store for analysis. You want to be sure your water chemistry is balanced and your chlorine level is back to normal before anyone gets back into the water.

Our Top Pick
AquaChek Select 7-in-1 Pool and Spa Test Strips
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Tests for 7 important chemistries in seconds: Total Hardness, Total Chlorine, Total Bromine, Free Chlorine, pH, Total Alkalinity, and Cyanuric Acid.

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7. Clean Your Pool Filter

The last thing you want is a filter full of particles slowly filling your pool back up with microscopic algae that could start another bloom. Deep clean your filter by soaking it in diluted muriatic acid, or simply replace it.

How to Use Flocculant to Remove Pool Algae

If you catch algae in your pool early on, you could use flocculant (also called floc) to save yourself some elbow grease. This additive bonds to floating algae particles, making it easier to vacuum them out of your pool.

Pool Flocculant Water Clarifier
$49.94

Pool floc binds particles (and dead algae) that are making your water cloudy together and sinks to the bottom of your pool so you can easily vacuum out the cloudy mess.

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If you have anything more serious than a mild green algae problem, we recommend you follow the full cleaning plan. For getting rid of a little green algae quickly, go ahead and get it the floc outta there.

  1. If you have a multiport valve on your filter, shut off your pump and turn the valve to Recirculate or Recycle. This will mix the floc around without filtering the water.
  2. Add the recommended dosage of liquid or powder flocculant to your pool.
  3. Circulate your water for two hours, then shut off your pump and let it sit overnight. The floc will bind to the algae, then settle on the pool floor.
  4. Turn the multi-port valve set to Waste so dirty water doesn’t blast back into your pool through your return lines.
  5. Hook up your backwash hose to the Backwash/Waste port. Direct your waste water appropriately.
  6. Vacuum your pool. Work slowly to make sure you get all the thick sediment off the bottom. If the water gets too cloudy, you may need to stop and allow the particles to settle again before continuing to vacuum.
  7. Add water while you’re vacuuming because you’ll be removing quite a lot.
  8. Double shock immediately after vacuuming to eliminate any remaining algae. You may also want to brush the pool sides and floor before shocking.
  9. Run your filter until the water clears.

Using Algaecide to Get Rid of Pool Algae

You may be wondering why we haven’t told you to use an algaecide to get rid of the algae in your pool. Even though some types of pool algaecide can kill algae, the product is much more effective as a preventive measure. Check out our Truth About Using Pool Agalecide article.

After cleaning and shocking your pool, wait for the chlorine to fall below five parts per million, then add a dose of algaecide. Brush your pool to loosen any last bits of algae you can’t see. The algaecide will kill it so it can be filtered out.

Our Top Pick
Pool Algaecide 60 (Copper-Free)
$27.97

A copper-free algaecide to help prevent your pool from turning green.

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Cleaning, Sanitizing, and Other Preventive Measures

Keeping up with the basics will also go a long way toward preventing algae.

Can You Swim in a Pool With Algae?

Pool algae is NOT harmful to swimmers. But pools with lots of algae is a great place for pathogens like E-coli. Algae spores find their way into your pool all the time, and while it can’t harm you, the bacteria feeding on it can.

Salt Water Pools Aren’t Immune to Algae

Are you wondering how to remove algae from a salt water pool? The process is exactly the same as for a chlorinated pool. Just remember to use calcium hypochlorite shock.

Calcium Hypochlorite Shock
$72.22
Use entire contents of bag when opened. If any granules settle to the bottom of the pool use brush to disperse. Add the recommended dosage of this product during evening hours while the filter pump is running.
Buy Now Learn More
If you click this link and make a purchase, we earn a commission at no additional cost to you. 10/25/2020 07:48 pm UTC

When Bad Algae Happens to Good Pools

Even if you’re on top of your pool water chemistry and regular maintenance, you may still wind up with algae. High humidity and wind are just two examples of contributing factors you couldn’t control even if you tried. But it’s important to act as soon as you notice algae in the pool because it can grow rapidly, becoming tougher to eradicate with each day it goes unaddressed.

If you leave behind even a small number of algae spores after cleaning and shocking, it won’t be long before they bloom again. So act quickly and aggressively to get rid of algae, then make algaecide application a part of your regular water care routine to keep the algae away for good.

Happy Swimming!

Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.

Frustrated by adding chemicals and trying to keep your pool clear all the time?

We cut out all the confusion of pool maintenance in this easy-to-read illustrated ebook and video course. It'll help you save $100 right away on pool care!

Click Here to Learn More
The Pool Care Handbook

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