Pool Care Pool Troubleshooting

How to Remove Algae Stains from Pool Walls

Algae stains are one of the many things that pool owners get to deal with after dealing with the nasty green, black or yellow organic matter called algae. Some stubborn stains may be left on the pool walls and other services when you remove the matter from your swimming pool. The bad news is, unlike other stains, algae stains don’t scrub off that easy – it doesn’t even respond to pool shock or algaecide and chlorine alone. So, how do you remove the stains from your swimming pool walls?

The best solution is to try and combine multiple algae stain-removing hacks, such as using the best, proven algae stain removers, scrubbing, and more. Cleaning your swimming pool with normal algaecide and pool shock might kill the algae but won’t cut it for you in removing the stains left. You might be forced to drain your swimming pool depending on the extent of the stain problem.

Companies continue to develop treatment solutions to make algae stain removal easy and seamless as possible. But before they can produce the magic cleaner, I have to keep you on tabs on the best way to clean algae stains from your pool surfaces and how to prevent them from occurring again.

What Types of Algae Stains Are There?

Before you can get to the central part of removing the stains, you might want to know the types of algae you might be dealing with during the cleaning.

Green Algae Stains

Green algae stains are the most common stains you will come across in your swimming pool, maybe because green algae grows relatively fast and can even turn your swimming pool green and cloudy in a matter of a day.

The stains start where the green algae grow most of the time, around corners and areas where those automatic pool cleaners can reach. It can also occur in pool areas where your pool water circulation is low and restricted areas like steps.

When the pool chlorine levels are low, the temperature warmer, and phosphate levels high, green algae growth gets boosted.

The best news is, you can remove green algae stains in less than 48 hours conveniently.

Mustard/Yellow Stains

The next common but less common than green algae is the yellow or mustard algae stains that exist as yellow or brown stains. It’s usually easy to brush away, but it does return easily.

It loves growing in shady areas protected from sunlight or those areas with limited circulation. Unlike green algae stains, it’s tougher to remove and resistant to normal chlorine levels.

For that reason, their removal might take you 72 hours.

Black Spot Algae Stains

Black algae aren’t that common, and if it happens to grow, it’s mostly confused with other matter such as dirt or mold. If it was to grow in your swimming pool, it could leave black spot algae on your pool walls. It spreads relatively slowly and appears as spots on the surfaces.

The bad news is, this type of stains can be challenging, considering black algae spores (roots) can penetrate even cement. If you don’t act quickly, you will be facing permanent damage and discoloration of your pool interior.

You should also know the cause of the black spot stains; black spot algae develop a protective layer on their surface, making them resistant to the sanitizer. Removing these stains is for sure challenging but doable.

How Do You Get Rid of Algae Stains from Pool Walls?

Even though there are three main types of pool algae stains, the process of removing them from your swimming pool is almost the same.

Yes, there are places where you will need to be vigorous or repeat treatment to be thorough. But, the whole process is quite similar.

Before you can start removing them, it’d be best, though, to figure out the type of algae stain you have in your swimming pool.

The stains can either be green stains caused by green algae, yellow or brown stains caused by mustard algae or metals, and black spots caused by black algae that can also exist as dark blue-green spots.

Now that you have identified the type of pool stains in your swimming pool, we can jump right into the main part, removing these stains.

What do you need?

  • Pool Test Strips, Liquid Test Kit, or a Digital Pool Test Kit
  • Green Stain Remover or Mustard Stain Remover or Black Algae Stain Remover
  • Pool Shock Treatment
  • Chlorine Tablet Holder
  • Stiff Nylon Brush or Wire Pool Brush

a) Test and Balance Your Pool Water

Before you can start scrubbing and forcing blisters on your hands, it’d be best to make sure your pool water chemistry chemicals are at the ideal levels.

Get yourself either pool test strips, a liquid test kit, or a digital pool test kit. You want to ensure the pool water pH is between 7.4 and 7.6, alkalinity between 100ppm and 150ppm.

Don’t worry much about the sanitizer levels as you will need to hyper-chlorinate the pool during pool shocking; the next step here.

b) Shock Your Pool

This is the main step of the pool algae stains removal process. You need to remember the type of pool algae you have in your swimming pool.

It’s important you understand your pool’s capacity when determining the pool chock dosage. If you don’t know-how, you can use my online pool calculator that simplifies everything for you.

Important: It’d be crucial you shock your pool in the evening or at night. Chlorine is sensitive to UV rays from the sun. It breaks it down, thus reducing its effectiveness.

Green Algae Stains:

If you have a small, green spot, a regular pool shock dose can do the trick. But if you have more than a spot, it’d be best to triple the dose.

Normally you’d need a pound of DryTec Calcium Hypochlorite Chlorinating Shock Treatment for a 10,000-gallon pool, which is enough during removal of a spot green algae stain.

But if you need to remove a strip of these stains, you will need 3-pounds of the same chlorine shock treatment.

Spray some green stain remover on the surface to accelerate the breakdown of the stains.

Yellow Mustard Stains:

The default dose for removing chlorine-resistant yellow stains is triple Shock Treatment dosage. However, you will need to combine it with brushing, which is the next step.

If the problem is advanced, you might want to give a quadruple dose. That ensures every mustard algae in the swimming pool dies and loosens from the walls.

Apply some stain remover agent to help loosen the stains from the walls.

Black Spot Algae Stains:

As aforementioned, black spot algae is the toughest to kill, and their stains will need vigorous treatment. One thing you should know, it’s not a true alga.

So, pool shock might not be as effective, but it can help break down its bonding. Add triple Shock Treatment and move to the next step.

Adding a black algae stain remover can make the whole process a lot easier for you. You can also try scrubbing the surface with a half chlorine tablet held using a chlorine tablet holder.

c) Brush Your Pool Walls

While the pool shock treatment and the algae stain removers do their thing, you will want to brush off the stains from the pool walls.

You need an ideal pool brush with stiff but safe bristles for your pool type. You have to go hard on the stains. Don’t worry; It can be your workout of the day.

If you have a fiberglass or vinyl swimming pool, the best brush to use is a stiff nylon brush. If your swimming pool is tiled or has concrete surfaces, then a wire pool brush is your best product.

Don’t be surprised if some stains don’t come off right away. Some might take days or weeks to come off.

d) Run Your Pool Pump

Start the pool circulation system and allows it to run for at least 24 hours for the pool shock treatment to be circulated to all the pool walls. If not, 24-hours, make sure the pump circulates for at least one turnover.

e) Brush the Pool Again

After the 24-hour circulation, brush the surfaces again and concentrate in areas with the algae stains. Don’t get frustrated if the stains still don’t come off as expected. As I mentioned, it might take a day or days to get the surfaces clean.

How to Prevent Algae Pool Stains on Your Pool Walls

Now that you know how to remove algae stains from pool walls knowing how to prevent them from occurring is crucial in removing them.

Maintain Ideal Pool Chemistry levels: Ensure your pool chemicals stay at the ideal levels to make sure algae doesn’t grow in your pool and cause stains.

Shock your pool regularly: Shocking your swimming pool can help make sure any algae spores that might have found their way into the water don’t grow. And as you well know, stopping the growth is the first step in preventing algae stains.

Invest in an Automatic Pool Cleaner: this type of cleaner will ensure your swimming pool surfaces stay clean all the time, giving the pool algae stains no place to settle.

Get a Manual Pool Vacuum: even though an automatic pool cleaner is the best option, it does miss some spots in a pool that can allow algae to grow. Using a manual pool vacuum, you can reach these spots, clean them and prevent the algae from growing, an effective way of keeping pool algae stains at bay.

Restore Your Pool Look – Remove the Nasty Algae Stains

Congratulations! You have successfully removed algae stains from your pool walls. It wasn’t that challenging. Right? Yes, a few steps will make you grow some muscles, but it makes you fit. Cleaning the nasty algae stains can restore your swimming pool look and give it a nice, inviting aesthetics.

About the author

Sharif Miah

Hi! I'm Sharif, the founder of Globo Pool® and I have been working in the pool & hot tub industry for the last few years. I love to share my experiences with people & hope you are enjoying my information and lessons!

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