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4 Causes of Algae in Your Swimming Pool (And What to Do About It)

4 Causes of Algae in Your Swimming Pool (And What to Do About It)

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One of the things that you might have noticed, especially if you are a frequent swimmer, is the presence of algae in a pool. Algae can be caused due to a variety of reasons and usually occurs due to a variety of reasons.

When you take a dive into the pool, the last thing that you want to see is a bit of green on certain parts of the pool, indicating the presence of algae.

You are probably going to be disgusted and might leave the pool almost immediately. Not to mention, the presence of algae also indicates that there’s something wrong with the filters in the pool, or that the water hasn’t been replaced or cleaned in a long while.

Now, there are a number of reasons why algae might start to grow in a swimming pool.

But, before we get to that, it’s important to understand what algae really is. Algae is basically a diverse group of aquatic organisms that are capable of producing oxygen through photosynthesis.

Algae generally lack true roots, leaves, or any kind of stems, nor do they have a properly developed vascular system that allows them to carry nutrients throughout their bodies or water.

A defining feature of algae is that many of them are unicellular, and usually show up in many different sizes or forms. Algae primarily make use of light energy to generate their own nutrition, and are also able to produce oxygen and other carbohydrates.

One of the main reasons why algae spreads so quickly is because it reproduces through its own spores. The spores can be blown in different areas and wherever it finds a suitable spot, it will start to reproduce.

If you have seen algae growing in ponds or on the corners of lakes before, you might already have realized that it requires a certain set of conditions that must be met before it is allowed to grow.

For starters, the water needs to be stagnant. Algae isn’t necessarily harmful to most swimmers, but it can create a very disgusting environment for the average swimmer.

After all, would you want to swim in a pool that’s covered with algae? Not only does it look disgusting, but it will also make the water dirtier.

Moreover, algae is also harmful for the pool. In case there’s algae present in your pool and you turn on the filters, there is a pretty high chance that the filter is going to get clogged.

Ultimately, the damage will be permanent and you might have to replace the filter altogether. Needless to say, a small lapse in judgement could eventually cost you a considerable amount of money.

Not only that, but simply removing the algae from your swimming pool is going to be difficult. As you can’t turn on the filter, you should know that it’s going to require a considerable amount of money and effort on your part to clear out the pool.

So, now that you know what algae is and just how harmful it can be, let’s talk about the major causes of algae in a swimming pool.

Causes of Algae in a Swimming Pool

Cyanobacteria algae, which is the most common type of algae that you will find; usually blue and green in color, occurs naturally. It is found in virtually all kinds of soil and plant debris.

As mentioned above, there is a strong chance that the algae spores can blow all the way into your pool, and can also be introduced into the pool by swimwear that hasn’t been properly cleaned.

For instance, if a swimmer had used the same swimwear while taking a dip in the ocean, there is a chance that algae spores might be introduced into the pool. In the simplest of terms, you should assume that algae is always found within the pool and is only going to bloom when a specific set of conditions are met.

So, what are these conditions?

1 – Poor Water Circulation

pH balance can help decrease algae

One of the main reasons why algae growth occurs in swimming pools is because of poor water circulation. You might not have realized it while swimming, but water continues to circulate throughout the pool on a consistent basis, moving from the pool into the filter and then back out again.

However, if the filter doesn’t work properly or if a smaller filter is used for a larger pool, there is a chance that dead spots are going to occur in certain parts of the pool. These dead spots or low flow areas can promote algae growth.

Algae needs still water to grow, so as long as the water continues to flow, you won’t have much to worry about. But, for larger pools, this is a bigger problem.

Regular testing needs to be carried out to determine whether the water is flowing consistently in all areas of the pool or if there are spots where the flow is considerably reduced or if a dead spot exists.

2 – Poor pH Balance in the Water

There are three things you need to check here, apart from the pH value: the alkalinity, cyanuric, and calcium levels. When was the last time the water levels were tested in the swimming pool?

A high pH value in the water indicates greater alkalinity, which, when coupled with the lower chlorine levels, could usually cause algae growth. You need to make sure these levels are balanced accordingly, because certain minerals, like calcium, actively work to combat the growth of algae in a swimming pool.

3 – Low Levels of Sanitation in the Pool

Incredibly low or inconsistent levels of chlorine in the swimming pool are probably the biggest reason why algae growth is promoted in the pool.

Chlorine, when added to the swimming pool water supply, creates a weak acid known as hypochlorous acid. This acid is able to kill bacteria such as salmonella and E. coli, and also kills germs that can cause harmful illnesses such as diarrhea or others.

Swimming pools across the globe are chlorinated. A number of different chlorine-based compounds are used for the process, ranging from sodium hypochlorite to chlorine gas and even chlorinated isocyanurates.

As these compounds come in contact with the water, they release hypochlorous acid, which does an effective job in keeping the water clean.

If the amount of chlorine in the water is low, it could quickly cause algae growth in the pool.

4 – Low Water Filtration

The water needs to be filtered on a regular basis. If you run the filter in the pool for a limited period of time, you need to consider extending the time period.

Similarly, if the water in the pool is more when compared with the size of the filter, you need to think about replacing it altogether.

Make sure you install an appropriately sized filter on the swimming pool to ensure that algae doesn’t start to grow in the pool.

Now, it doesn’t matter how the algae was introduced, you will want to get rid of it as quickly as possible. The most noticeable sign that there’s algae in your pool is water discoloration.

Depending on the kind of algae that is infecting your pool, the color might vary. It could be either blue-black, yellow, or even green.

Now, let’s talk about the best methods that can be used for cleaning the algae.

How to Get Rid of Algae in Your Pool

Manual Vacuuming Is the Best Solution

Vacuuming can help decrease algae

Most people make use of automated or robotic pool cleaners to keep algae out. However, you should know that these aren’t really as effective, and there is a chance that these automatic cleaners might miss out clear spots.

Instead, you should consider manually vacuuming the area directly and dump the whole thing directly in the waste.

This way, you will be able to bypass the filtration system and prevent any kind of recirculation of the contaminated water. When you vacuum manually around the pool, do make sure that you focus on areas with dead spots so that you can get rid of algae spots.

Brush the Pool Properly

Pool brushing can help improve algae

The algae might end up settling on the walls of your swimming pool. You need to make sure that you scrub it off the walls properly so that when you add sanitizer in the mix, it is able to penetrate deeply into the remaining algae.

Moreover, when you brush up the walls properly with a good quality brush, it will help you stir up all the sediment that has gotten lodged in the pool walls.

A stiff pool brush is usually a good choice, and can be used on the walls of the pool and the floor. Corners and other shaded areas need to be carefully brushed, as the chances of algae growing in those areas is considerably higher.

As you continue to clean it, the water is going to get more and more cloudy, which will also obstruct your view. That is one of the main reasons why you should start with these areas.

Balance the Water and Test it on a Regular Basis

There are a bunch of different tools available to you that can be used to test the water. There are digital kits, as well as testing strips that can be used to determine the pH value of the water.

Not only that, but you can also test the alkalinity and then decide whether the chemistry of the water is right or wrong.

We have already talked about the ideal conditions for algae growth, so you need to balance the water chemistry in a way that it helps keep the algae away. When adding sanitizer to the water supply, you need to first check whether the sanitizer is effective against killing algae.

If you are using a poor quality sanitizer, it’s probably not going to be enough for getting rid of the algae. Low alkalinity, also known as a higher pH value, will help reduce pool shock considerably.

Shock Treatment

There are certain types of algae that require shock treatment to get rid of the problem. If you haven’t used chlorine shock before, it’s best if you consider using calcium hypochlorite shock.

If the infection is heavy, it’s best if you consider using hypochlorite shock. The package instructions are usually mentioned at the back, and will help you determine the amount of shock you need depending on the size of the pool.

Stabilized chlorine isn’t a wise choice for the pool as you will probably end up with an excess of cyanuric acid. This will prevent the effectiveness of your stabilizer and will also allow algae right back into your pool.

On top of that, it could also lead to more complicated problems.

Filter it Out

When the shock treatment ends up killing the algae, the water in the pool is going to turn a cloudy blue. You will need to run the filter consistently for around eight hours to get the algae completely out of the pool.

To speed up the process, you should consider adding a bit of pool water clarifier. Before you turn on the pump, it’s also recommended that you check whether the supply of water is enough or not.

Clean the Filter – Don’t Rinse It

Clean pool filter to decrease algae don't just rinse

A common mistake that most people make when it comes to cleaning out the filter is that they end up rinsing it thoroughly. You don’t want the filter slowly releasing particles back into the pool, which would again manifest in algae as soon as the conditions are met.

Instead, you should consider soaking your filter in diluted muriatic acid to get rid of the microscopic particles.

These are just a few things that you should know about getting rid of algae from your swimming pool. It’s going to require a bit of effort on your part, but it’s important that you take action quickly to minimize the algae from spreading.


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