How To Get Rid Of Algae In A Pool

If you hang out by swimming pools or even beaches a lot, you’ve most likely stepped on algae at one point. 

A Must-Read: Best Pool Accessories

Algae is a living organism that feels feathery, slimy, and not to mention slippery. They are a fairly common sight in swimming pools, so don’t be alarmed when you encounter one. 

Instead, you should learn how to get rid of algae. But what exactly is algae and how does this organism work?

What Causes Algae To Bloom? 

Great news for salt water pool owners: algae blooms are less prominent in saltwater than in it is on traditionally chlorinated pools. 

However, that doesn’t exempt you from actually having to deal with algae. 

At a certain point, you’re bound to miss regular pool cleaning schedules. When that happens, your pool’s pH balance might get thrown off. This creates a perfect environment for algae to bloom. 

Beyond imbalanced water chemistry, there are loads of other things that can cause an algae infestation such as: 

  • Warm weather
  • Poor circulation
  • Low free-chlorine
  • Nitrates & CO2
  • Wind
  • Rain
  • Contaminated equipment or swimsuits

Put all these together, and they make the perfect recipe for an algae bloom—and at a rapid state, that is.

Types Of Algae And How To Get Rid Of Them

Algae is an umbrella term for organisms that use photosynthesis to produce their own food. They highly vary in size, ranging from unicellular (Chlorella, diatoms) to multicellular (giant kelps, large alga).

Species of algae are so diverse that they span over 21,000 varieties. In the realm of swimming pools, however, they are simply just identified through colors to avoid confusion. 

That said, an assorted mix of algae can infest the pool. Let’s get to know each one of them. 

Green Algae 

Perhaps the algae we may all have seen (and stepped on—ew!) at one point is the green algae. That comes with no surprise, though. It’s the most common among all the algae found in swimming pools and spa surfaces.

Green algae typically appear when there are high pH and lack of filtration and sanitation. You can find them floating around the pool or clinging onto walls. They come in a variety of hues from blue-green, to yellow-green, to dark-green. 

Get rid of it! Use chlorine or algaecide to destroy green algae from its root. Do not just wipe it off. Even if you think you’re the best cleaner in the world, green algae will just grow back in a matter of hours. 

Attack it while it’s on its early stage—that is, when you start to notice green patches appearing in the corners. They multiply quickly and before you know it, they’ve already dominated the entire pool area. 

The bright side to all of this? At the very least, green algae is the easiest to encounter and easiest to kill. 

Yellow Algae 

Yellow algae are also appetizingly referred to as ‘mustard algae’ due to its dull yellow shade. They typically appear on the isolated corners of the pool where no sunlight hits. 

Because of their color, yellow algae or ‘mustard algae’ can be easily mistaken for dirt or sand. They are also pretty hard to kill considering their high tolerance to chlorine. In other words, they are as stubborn as a goat. 

Get rid of it! Simply attacking them with algaecides or chlorine won’t work on these pesky plants. Save yourself the time and use a shock-treatment to destroy green algae from its root. Simply wiping it off or dousing with chemicals won’t be enough. 

Another way is to deal with them through brute force by vacuuming them straight out of the pool. 

But to do this, you would need to brush them all first then floc them so the algae spores can clump together. This makes for easier and cleaner vacuuming to avoid leaving out algae residue. 

Make sure to leave the pool spotless when dealing with yellow algae. They can be very stubborn, with particles able to cling to pool accessories and equipment even soon after treatment. 

Black Algae 

Even tougher than the yellow algae is the black algae. They grow roots that can travel deep into the plasters of your pool wall and have protective layers on the surface. 

Apart from that, they usually appear as black or blue-green spots the size of mint candies up to the size of a quarter.

Unless you succeed in completely annihilating their roots, expect a new head to grow back from the root. 

Also, that protective layer mentioned a while ago? Its sole purpose is to make life harder for you. Thanks to the protective shield, black algae is highly resistant to algaecides and chlorine, much like yellow algae. 

Just looking at and hearing the term ‘black algae’, you already know you have massive cleaning to do. It’s like cleaning cavity that’s been left untreated for a long time.

Get rid of it! Brush religiously and then turn up the shock treatment extra strong. Scraping off the algae first will allow you to break through the algae slime, making the chemical process a lot easier. You really have to go double-whammy on this one. 

Pink Algae 

Not at all part of the algae family, rather, a bacteria commonly known as ‘pink slime’. True to its name, they appear slimy with a hint of red or orange hue. 

Pink slime thrives in a low-chlorine environment and is commonly found in smooth surfaces. They grow rather slowly and don’t really multiply at a large scale compared to algae. 

However, pink slime is highly resistant to chlorine. Don’t bother with it. 

Get rid of it! Instead, simple brushing is enough to keep them off, along with routine pool maintenance. 

What Happens If You Don’t Get Rid Of Algae? 

Algae by itself is relatively harmless, so why bother cleaning it? 

First off, it’s just downright disgusting. The slimy texture, the muddy look, everything about them does not fit in with the serene and sterile ambiance a swimming pool gives off. 

They do, however, come with several health issues. 

Swimming in an algae-infested pool can give you all sorts of infections—especially if you have an open wound. You can also get rashes and allergic reactions due to the bacteria surrounding algae. 

There’s also a higher chance of physical injury when swimming in pools overwhelmed with algae. It can get extremely slippery because of the slime coat. 

It’s not really worth it to take a dip if you see a sizeable amount of algae surrounding the pool. 

Preventing Algae Growth

You can never really achieve a full, 100% algae-free swimming pool. There will always be a particle microscopic enough to get by unnoticed, and that’s totally fine. 

What’s important is to never let algae significantly clog the areas of your pool. 

The key to that is all in the environment. Keep the pool’s chemical balance in check. For instance, since green algae thrives on poor circulation and low chlorine-count, address that by improving the circulation and chemical make of your pool. 

Manage and maintain your pool regularly to create conditions that are anti-algae by keeping the pool clean and usable. 

So, let’s get to the specifics. 


This alone will definitely not get rid of algae completely. However, this step plays the most important role in thoroughly cleaning your swimming pool. 

Brushing off every nook and cranny where algae is present is crucial to completely eradicating them. This is also where most of your effort goes, so make it count. Be keen on tricky areas such as ladders and other hard-to-spot crevices where algae may be hiding. 

Use a nylon brush if your pool has a vinyl liner. On the other hand, a steel brush works better on a concrete pool. 

Also, when dealing with very stubborn algae-like black or yellow algae, it’s best to use a pumice stone because of its hard and rough surface.

Pool Shock 

Also known as ‘super chlorination’, this method basically leaves your salt chlorinator on full blast for a whole day. The result? Shocking the pool with incredibly high amounts of chlorine. 

Seasoned pool owners know there are appropriate times when to use a pool shock. Algae is one of the reasons why. While green algae are easily dealt with algaecide, yellow and black algae are highly intolerant to chemicals in general. 

Hence, a strong pool shock is needed in order to completely get rid of all types of algae. 

For saltwater pools, a lithium hypochlorite shock might be heaps better than a calcium hypochlorite one. 


The purpose of flocculants is to help gather the algae together so they’re easier to vacuum afterward. 

Flocs are made of a gel-like substance that attracts particles like algae. They do mess up the chemistry of your pool, though. 

It’s important to follow up with a chemical balance check after using your flocculant. 


Consider this an additional step for further preventive measures. Algae can be really stubborn and persistent. Adding another line of defense helps seal the deal and make sure they won’t be back. 

Test Water 

After shocking and using the flocculant and algaecide, it’s time to test the water after 24 hours of circulating. 

If you see white or grey dead algae floating at the surface of the pool, then the procedure was successful. You may also notice a cloudy surface on your pool when this happens. 

You might as well also want to double-check your chlorine and pH levels just so you can diagnose your pool. 

Vacuum and Clean Filter 

If the procedure was only partially successful and you still see algae floating around, you may want to brush again and vacuum.

Be patient and wait for a few days before you can fully see significant improvement. Your balanced pool chemistry will take care of that. At the latest, wait until day 3. 

Once the coast is clear, give your pool one last go with the vacuum just to secure everything and make sure that the pool is spotless. 

The final step, douse your filter with muriatic acid to completely clear out all the stuck algae.

Wrap Up

Algae are a painful reminder that not all pools are perfectly spotless. However, remember that you have more than enough control when it comes to managing their growth.

Keep your pool chemicals in check as much as possible and never neglect your pool equipment and accessories. Algae are very stubborn and sneaky!

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