Are Pool Algae Harmful? Is it Safe to Swim in a Pool With Algae?

One of the main problems that we must solve in a pool is the appearance of algae. But are the algae dangerous for people, and is it safe to swim in a pool with algae?

Pool algae is a kind of fungus that lives in pool water and grows due to a lack of proper pool sanitization. The primary pool algae types are green algae, black algae, and mustard algae. They are usually harmless, but sometimes pool algae can be dangerous for humans.

So, today in this article, we will discuss whether pool algae is harmful to humans and whether it is safe to swim in a pool with algae?

What are pool algae?

Algae is a living organism that begins to multiply rapidly on warm, sunny days.

Algae spores are constantly introduced into the pool by bathers, wind, rain, or contaminated equipment. The algae appear suddenly as soon as the conditions are right in your swimming pool.

This type of plant contains chlorophyll and uses photosynthesis to grow. Thus, they absorb carbon dioxide and release oxygen as a by-product. 

The most common algae in swimming pools are Chlorophyceae, known as green algae.

Causes of algae growth

The pool is an excellent breeding ground for microbes and algae. And if there is nothing that prevents them from multiplying, then the water in the pool will bloom.

Filters do not trap microorganisms, so filtration alone cannot solve the problem. This applies equally to the small summer cottage pool and the Olympic pool.

There are various reasons why pool algae form. These are:

  • Your water is not sufficiently or correctly treated: The pH of the swimming pool water is poorly balanced, the disinfectant does not work, or it is used in small quantities.
  • Your pool is poorly maintained or cleaned.
  • The filtration of your swimming pool water is working poorly or not for long enough, the filter or the pipes may be clogged.
  • The temperature is too high: The hot weather promotes algae development in the water.

Let’s see what types of algae can occur in your swimming pool and which of these are dangerous.

Types of algae in a pool

There are more than 21,000 known types of algae. However, it is hard to recognize every species.

It is sufficient to know the most common types for a productive battle against algae growth in your pool.

Green pool algae

Green pool algae are usually not dangerous for humans, but they indicate pool equipment problems and lack of pool maintenance.

Chlorophyte pool algae are the most common green algae in pools because the pool water contains high nitrogen compounds, promoting green pool algae growth.

But green algae also grow when the pool water pH level is too low or high or when the pool water temperature is in the range of 68-86 degrees F.

Your water turns dark green, the filter is clogged with green algae, and the pool walls are slippery.

The problem with green algae is that it uses up enormous amounts of chlorine. A vicious circle arises if you are not careful.

Yellow swimming pool algae

Step by step, the yellow algae (mustard algae) covers the dividers and lower part of the pool with a consistent film.

Fortunately, the mustard algae are easy to clean but, you can spend the entire swimming season battling yellow-green growth.

The smallest oversight and the film dissipated all through the whole water section. 

It is important to continually keep an expanded degree of chlorine in your pool water during the battle. 

Dangerous black algae

The black algae are dangerous for humans and animals, and bathing is not permitted during an infection.

Black pool algae live in warm water and multiply rapidly when the pool water is treated incorrectly or not at all. They can be found in any pool that has an anaerobic pool environment.

Problems with black algae appear in your pool as dim, dark, or blue/green spots, around 5 millimeters big.

Their foundations dive deep into the concrete, in the joints between the tiles, and assuming the roots are not totally obliterated, another black growth cap will develop back in a similar spot.

Pink algae

This isn’t an algae in essence, yet a type of microbe.

They typically show up as spots or stripes in corners, close to inserted components, in broken concrete. These types of pink algae grow gradually and will probably not fill the whole pool.

However, you have to get rid of this type of microbe as quickly as possible.

White algae

It is conceivable that white algae are a type of pink, green growth. They grow like mushrooms up to 5 centimeters in measurement, and in most cases, the reason for the appearance is a low pH level.

In particular indoor pools are affected by this type of algae.

Generally speaking, they show up in pools treated with dynamic oxygen. They grow anywhere there is practically zero water stream.

For instance, under fronts of floodlights and counter-flows, behind steps on the dividers of the pool, on the base surface of steps.

Is Pool Algae Harmful To Humans?

Algae itself is not harmful to bathers, but it can become a breeding ground for large quantities of pathogens such as E-coli bacteria.

So pool owners should take necessary steps to eliminate pool algae using chemicals or pool algaecides.

Pool algae are the result of ineffective pool cleaning and maintenance practices.

The first and foremost problem is that swimming in an algae pool is not very pleasant. The second problem is that it takes a lot of money to fight algae and a lot of effort to completely get rid of the pool water.

Algae clog the filter media in the sand filters, reducing the efficiency of the filtration system and requiring more backwashing or partial replacement of the filter media.

In addition, chlorine, which should act on other pollutants, is oxidized by algae. Respectively, the chlorine level in the pool water is sharply reduced, which inevitably leads to cloudy water and the appearance of an unpleasant odor.

Algae can be compared in part to the weeds in your garden. Unsightly, unwanted, unknown where they come from, create additional problems for the pool owner, and ruin the fun.

All of the above makes it clear that the correct actions are important to kill the algae in your swimming pool.

What Are The Diseases Caused By Algae?

Dangerous toxins released by blue-green algae cause neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and Lou Gehrig’s disease.

It should be noted that bathing in a pool with algae can lead to rashes all over the body. Itching, reddening of the skin, irritated mucous membranes of the eyes and nose can occur.

If such water is swallowed, an increase in temperature, abdominal pain, nausea, and vomiting may occur.

Pool water is transparent, and algae are usually not visible to the human eye in a pool. But it can be seen that pools with algae are not bright and do not shine in the sun.

This is why pool owners should invest in an algaecide pool treatment and pool shock or bleach.

Is It Safe To Swim In a Pool With Algae?

Pool algae are not harmful to humans. But I advise you not to waste time, since the treatment will be more effective if you do it as soon as possible.

The water is getting greener and greener, and bathing in cloudy water is not recommended.

Green algae are not dangerous, but I recommend avoiding bathing in a contaminated pool. Bathing in a clean pool is much more enjoyable.

Even the purest water contains a minimal amount of bacteria and algal spores. With favorable factors, they are capable of multiplying like an avalanche, which will require the adoption of certain measures from the owner of the pool.

So, It is crucial to keep your pool clean to avoid diseases and bacteria.

Do you have further questions about pool algae?

Contact me on Twitter at @contactswimfool. I am happy to help you.

Have fun cleaning your swimming 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, 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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