Mustard Algae: Why You Need to Watch Out

Being a pool owner has its benefits. You can relax by the pool or swim to beat the heat. But the unavoidable responsibilities of maintaining hygiene and regular cleaning make it a challenging task.

Moreover, if you are the owner of a swimming pool, mustard algae must be one of the nightmares to deal with. It is pretty challenging to get rid of mustard algae, and you have to take measures to eradicate it from the pool repetitively. 

In this article, I will discuss the possible ways to prevent algae in your pool and how to get rid of it for good. So, keep reading!

What Are Mustard Algae?

They are also referred to as “yellow-green algae” or “yellow algae” and are identified by their unique color and texture.

Yellow algae are different from green algae. While the green algae are limy in texture and stick to the pool surface, the mustard algae are finely granular or powder-like. They often get mistaken for dirt or debris or the stains seen on the pool walls.

Moreover, mustard algae possess the ability to resist chlorine. Mustard algae can survive without water, and so they get transferred from the pool to the bathing suits and pool toys, and other pieces of equipment. The more they spread elsewhere, the more difficult it becomes to eradicate them.

From Where Does Mustard Algae Come From? 

Mustard algae mostly grow in warm climates and thrive in freshwater. They spread fast through their migratory tendency. 

The microscopic cells of algae often spread into pools through swimsuits, hair, or water toys. If you swim in a lake or river replete with algae and then sim in your pool, you are likely to carry algae into the pool.

Again, if common pool equipment is used for different pools, it may spread from another algae-laden pool.

What Is the Impact of Mustard Algae in A Pool? 

Mustard algae make your pool look dirty as their powdery surface resembles dirt stain or pollens or debris on the pool walls. Thus, the unclean pool looks unhygienic and also leads to the clouding of water. 

Therefore, it becomes difficult to maintain the quality and clarity of the water in the pool. The balancing of water also gets affected and impacts the longevity of the pool equipment and the filter. Thus, the cost of maintenance goes up for repairing the filter or testing the chemicals in the pool.

If the pool is infested with algae, they make the pool hospitable for other harmful microorganisms and bacteria. This aggravates the problem as they also pose a severe threat to health. Hence it is compulsory to get rid of mustard algae from the swimming pool.

How to Spot Mustard Algae?

They have a distinctive mustard yellow color which confers the name mustard algae. However, the color ranges from bright yellow to deeper or darker mustard yellow. They often look like the yellow pollen from the flowers with its powdery and dry texture. 

The algae find the following condition hospitable:

  • Warm climate
  • Shade
  • Still water

Hence, they are likely to be seen at the bottom of the pool or the pool’s walls.

Although it seems that in the pools with good exposure to sunlight or proper water circulation, algae may not grow, yet they are found in corners of the wall, the small hidden dead spots, shaded areas of the pool lights even the ladder. 

These are difficult to remove. By scrubbing or brushing the surface temporarily, they get swiped away. Still, tiny particles cling to these surfaces, and they gradually thrive, and thus, more intensive methods are needed to remove them instead of mere scrubbing.

Can I Prevent Mustard Algae from Growing into My Pool?

Yes, it is possible to prevent mustard algae growth in your swimming pool. However, the process is lengthy and quite laborious. If your pool is replete with mustard algae, it is a time-consuming task to eradicate them.

There are several methods to remove it with precision. In the worst-case scenario, you will have to drain out the water and subject the pool to acid wash. This will consume a lot of effort and time.

Hence, it is advisable to stress preventive measures to evade such a situation. You can take the following steps:

●       Testing the Water

Firstly, it is essential to ensure the balance of pool chemistry. The pool water should have the chemicals and the pH level, chlorine, etc., in the perfect amount of balance.

You must check the alkalinity and the calcium hardness as well. You may use a pool chemistry kit or a test strip to get an idea about the quantity of the chemicals in the pool.

Ideally, in a pool, the pH level should 7.4. However, having a pH level of 7.2 or 7.6 may be accepted as well. It is essential to maintain the required pH level because an increase in its level would make the environment even more hospitable for mustard algae. Thus, you must do pool testing at regular intervals to keep the pH in control. 

If you wonder how to control the pH, you may try adding muriatic acid or sodium bisulfate in an appropriate quantity. This will lower the pH level effectively. The fluctuation of pH has an impact on the alkalinity of the pool as well.

Again, the alkalinity of the water should be between 80 to 140 parts per million. Since it is directly dependent on the pH, it is crucial to monitor the pH level. To ensure the stability of the chemical level and controlling alkalinity, pH should be controlled.

●       Shocking the Pool Regularly

Socking the pool will guarantee the removal of unwanted microorganisms from the pool and prevent algae growth. Pool shocking includes the process of chlorinating the pool. It will also clean the water and remove its cloudiness caused by the algae.

Before opting for pool shock, you must survey the market and resort to using the best products. It is an easy process and can be done every week to attain the best result. However, you should stick to the instruction guidelines mentioned in the product.

●       Keep the Pool Surface Crystal Clear and Clean

The ideal way to prevent the growth of algae is to maintain hygiene and cleanliness. If you can keep the pool surface clean, it would lessen the chances of algae -growth. You may resort to the use of a robotic pool cleaner to ensure maximum efficiency.

It cleans the pool thoroughly by scrubbing the surface but also the minute space between the tile lines. It brushes the entire surface and removes debris and leaves meticulously.

Since the robotic pool cleaner can detect the silt-like texture of the debris in the pool, it can locate the mustard algae and remove it.

●       Run Your Pump and Filter

Water circulation is needed to avoid algae from settling on the surface of the pool. 

Algae prefer stagnant water, and thus, steps should be taken not to allow water stagnation. Hence, you can regularly run the pool’s filter and the water pump for around seven to eight hours. This will keep the water circulating.

How Can I Get Rid of Mustard Algae?

If your pool is in a deplorable state, you need to put in greater effort. If the yellow algae are clinging onto the walls of your pool for a longer period, your task of removal shall be more challenging.

Here are the steps that you need to follow to get rid of mustard algae.

Disinfecting the Pool Accessories

This is the most crucial step that cannot be avoided. If you make the mistake of skipping this step, your mission will be futile. 

It is compulsory to disinfect the pool accessories like the bathing suit, goggles, pool toys before entering the pool. After disinfecting all these items, they must be exposed to a hot setting to dry sufficiently for maximum safety.

Again, you should clean the pool accessories with a chlorine solution before use. This step of disinfecting these items prevents any algae particle attached to these to again enter the pool.

Brushing the Pool

Algae being stubborn, chlorine resistant, and difficult to remove, several measures are to be taken to ensure their permanent removal. 

After that, brushing and scrubbing of the pool surface should be done diligently without leaving any portion.

The hidden and challenging to reach areas where algae stay attached like the stairs of the pool or beside the gasket.

Vacuuming the Pool

This is another mandatory step that has to be done after the scrubbing and brushing of the pool surface.

This assures the loosening of the algae spores in the pool. It removes all dirt and debris as well. 

Vacuuming the pool will allow all dirt to wash away with the water and pass away through the filter down the waste line.

Test pH Level

After vacuuming, you must check the pH level of the pool. For this purpose, you should use a reliable testing kit to acquire an accurate reading of the pH level.

If you find that it lies between 7.2 to 7.6, it will denote that the mission successfully received the reading.

If the reading shows greater pH, you conduct the cleaning process again to attain better results.

Clean Pool Filter

After the water drains out the algae through the filter, it is compulsory to clean the pool filter. It may also happen that some algae particles may get attached to the filter. It would again ensure the re-entry of the mustard algae in the pool. To evade this situation, the filter has to be cleaned thoroughly. 

The instruction manual of the product must be followed while cleaning the filter. Moreover, if the filter is a D.E filter or a sand filter, it is advisable to backwash them.

Shock Your Pool

Finally, depending on the state of the pool, you must shock the pool. The frequency of it is based on the presence of mustard algae even after following the other steps.

However, the efficiency of the shock treatment is directly proportional to the success of the previous steps. So, if the previous steps were not much successful, you have to repeat this pool shock step. You must again disinfect the pool accessories.

Once you successfully eradicate yellow algae from your pool, you must not become complacent, as algae may return easily. Instead, you should focus on preventive measures and evade any further algae invasion in your pool.

What to Do After Pool Treatment?

If you follow all the above-stated steps to get rid of the mustard algae, you will be able to eradicate the stubborn stains of yellow algae successfully. However, you must not skip any step; instead, follow them all.

After the treatment of the pool, you have to vigilant about the condition of the pool and the pool chemistry. Ideally, you must test the pool water and check the pH levels regularly, along with the alkalinity and the calcium hardness. The chlorine level should be optimum in the pool.

After the pool treatment, you must allow the pool filter to continue running almost all day long for the next few days. After a few days, you can reduce it to around eight to nine hours per day. This will keep the water circulating and prevent any stagnation.

Finally, the regular maintenance of the pool must be stressed. You must daily scrub and brush the surface to prevent the settlement of any microorganisms on the surface and walls. After that, it must be repeated by again vacuuming the pool. You have to use an algaecide within around seven days of shocking pool treatment. These steps will ensure the cleanliness of the pool and keep it free from the onslaught of mustard algae.


The steps mentioned in this article are lengthy and repetitive. It is time-consuming and requires a lot of effort as well. However, to ensure good health and clean living, you have to resort to these steps. 

I hope this article clarifies your doubts about mustard algae. Now you can commence this mission of getting rid of yellow algae and make the pool safe for regular use.

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