Pink Slime in Pool: How to Get Rid of Pink Algae in Your Pool

Have you discovered pink algae in the pool and don’t know how to get the pink slime out of the pool water as quickly as possible?

The pink algae are actually not algae, but bacteria that can be easily recognized by the pink to pinkish-red biofilm as a deposit in the pool. The pink algae stains can easily be removed from the swimming pool with a pool brush, a little chlorine, and a filter run time of 24 hours.

In this article, I will explain how pink algae are formed, what they are, and how you should clean the pool.

Pink slime in the pool. What is that?

Pink algae in your pool are actually not algae. Much more, it is – like the black algae – a bacterium (Serratia marcescens).

This type of algae – or the biofilm – is interestingly referred to as pink slime in the US.

The pink algae can often be found on the ground as deposits, but the water line in the pool or the pipe systems are not spared either.

But how do these bacteria get into the pool, and why are they reddish?

An infestation by the pink or green algae in the pool can have various reasons.

The bacterium may have been brought in from the environment or by a person via droplets. In addition, the growth of pink algae in the pool is favored due to insufficient water treatment and adverse weather conditions.

The pinkish coloration (hence the name pink slime) only appears after a disinfectant such as an algaecide or chlorine has been used.

Before that, the bacteria were not visible and were only noticeable when the pool was suddenly slippery and greasy.

As a result of the disinfection, the bacteria die and leave a reddish color.

A pink-red biofilm is also discovered as a deposit in the pool.

If you have pink bacteria in the pool water, the pool filter is likely also affected.

That means: A complete pool cleaning is necessary to remove the pink algae from the pool in the long term.

I will explain exactly how this works earlier in this blog article.

Instructions: Remove pink Slime in the pool

You don’t have to despair if you see pink algae – or something that looks like white mold – in the pool.

The pink algae can be removed quickly with my practical tips and little effort.

Before we start, you need to prepare the following pool equipment beforehand:

  • A pool brush to loosen the pink slime.
  • Liquid chlorine for shock chlorination.
  • Some of the algaecides for disinfection.
  • Ideally, a simple pool vacuum.

Tip: You can find my recommendations via the links, which you can possibly buy online.

Do you have it all together? Then you are ready for the pool cleaning part.

1. Clean the filter beforehand

If the pool filter turns pinkish, then it is because the bacteria are also present in the filter.

To make pool cleaning as effective as possible, you must first clean the filter sand or the cartridge filter.

In the case of a sand filter system, it is sufficient to carry out a backwash with subsequent rinsing.

A slightly soiled cartridge filter can be rinsed off with a high-pressure cleaner, or the filter can be replaced if necessary.

2. The pool water treatment

Next, test the pool water with test strips or an electronic water tester.

Ensure that the pH value is between 7,2 and 7,6 because an exact pH value promotes pool cleaning in the next step.

You can use a pH plus or a pH minus for this purpose – you can find a recommended product on Amazon via the links.

Tip: Be sure to put on old clothes and, for safety, gloves when using the acids.

3. Shock chlorination of the pool (pool shock)

Professionals remove the pink biofilm in the pool with simple shock chlorination.

Here you can use 1 kg of rapidly dissolving chlorine per 25 m³ of water.

In a rectangular or round pool, the volume of water is easy to calculate. But if you have a free shape or a kidney shape, then the pool’s volume needs to be roughly estimated.

Then let the pump run for 24 to 36 hours until the water clears again.

You can only go swimming in the pool again when the chlorine value is below 1.5 ppm.

Tip: It is best to perform the pool shock late afternoon or evening. The reason for this is the susceptibility of chlorine to the sun’s UV rays

4. Scrub the pink slime in the pool

While the filter pump is still running – immediately after the shock chlorination – you take a pool brush in your hand and scrub the entire surface in the pool.

Do not miss any spots. Otherwise, the pink algae may form in the pool.

You should scrub thoroughly, especially in the corners and other difficult areas, so all bacteria are chased through the filter.

In the meantime, scrub the pool 2 or 3 times. Two is Better!

Tip: If necessary, use a small sponge with which you can remove the biofilm from the surface.

5. Vacuum the pool

If the filter does not completely capture the dirt on the pool floor or in the corners, then you can try to adjust the nozzles.

If that doesn’t help either, you can vacuum the pool with a pool vacuum.

The only important thing here is to set the filter to Empty.

You lose some water in the process, but this way, the biofilm, and remaining pink algae do not get back into the water cycle of the pool.

Later the water level in the bath is raised with fresh water so that the pump does not suck in air.

When the pool is filled, the water values change, but that doesn’t matter because the values have to be adjusted again after the shock chlorination.

6. Apply an algaecide against the pink algae

The algaecide is a good means to inhibit the growth of pink algae.

Add some algaecide to the pool and always observe the manufacturer’s instructions.

Please don’t overdo it, as too much of the algicide can be harmful and lead to foam in the pool.

Tip: Usually, an algae killer is not always necessary, but correctly dosed it can contribute to improved water quality – you can find out more in my blog.

7. Clean the filter again

Next, you should clean the filter again and possibly use a filter cleaner.

This step is how we make sure that there is no pink biofilm (bacteria) left – after all, you don’t want to go through the whole procedure again?

8. Test and optimize the pool water

The last step is to test the pool water again.

As already mentioned, you can use test strips or an electronic water tester to do this.

In the process, it is important that the following parameters ​​are measured and optimized accordingly:

  • pH value: 7,2 – 7,6
  • Alkalinity: between 80 and 120 ppm
  • Calcium: 200 to 400 ppm

Are pink algae dangerous in the pool?

Are you wondering if the pink algae in the pool are dangerous?

The pink algae – the Serratia marcescens – are assigned to risk group 2 by the Biological Agents Ordinance and are dangerous in the pool.

In addition, the ordinance, in conjunction with the technical rules for biological agents, stipulates that these bacteria can cause diseases in humans. Source.

The bacterium is negligently described as harmless in alleged pool maintenance guides, although scientific studies have shown otherwise.

I am not a scientist, but such grossly negligent information must not be!

Widespread distribution in the population is rather unlikely, but the following symptoms of illness due to the pink algae may still occur:

  • an infection of the urinary tract
  • pneumonia
  • sepsis

Therefore, you should start removing the pink algae in the pool as soon as possible.

Don’t wait until you see a biofilm in the pool.

For this purpose, I want to list a few preventive measures against pink slime – read on in the following chapter.

Permanently prevent pink algae in the pool

You now know that the pink biofilm in the pool can be harmful to your health.

I also explained to you how the pink slime could be removed from the pool, but if it’s up to me, then you shouldn’t let algae develop in the pool in the first place.

Here you will find suitable measures how to prevent pink slime in the pool permanently.

  • Scrubbing the pool regularly: Make sure the pool is cleaned regularly with a pool brush. Ideally, this should take place daily. You can make pool cleaning easier by using an electric pool cleaning robot against algae.
  • Optimize the filter run times: Nothing promotes algae growth as much as a filter run time that is too short. The water in the pool should run through the filter 2 to 3 times a day, especially on hot days in June, and for this purpose, the pump must run for 6 to 8 hours – depending on the performance. In the case of small cartridge filters, an endurance run is even called for.
  • Constantly producing free chlorine: Chlorine is a good disinfectant against pink algae. Use a dosing float and insert chlorine tablets in these. That way, you can’t optimize the chlorine value perfectly, but you get very close to the value.
  •  Algaecide: The algaecide are not only there to kill algae but also serve wonderfully to inhibit the growth of algae. The application does not even lead to the pool becoming greasy and slippery due to the biofilm. I have explained in detail in my blog how to use the algaecide correctly.

Do you have any further questions about pink algae in the pool?

I recommend that you browse my helpful blog or contact me at @contactswimfool on Facebook, Twitter, or YouTube – I’ll be happy to help you personally.

With that in mind, have fun eliminating the pink slime in the pool.

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Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

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