Can You Swim in a Pool with Mustard Algae?

Mustard algae can be a nuisance when it appears in your swimming pool, often presenting itself as small, yellow patches on the pool’s walls and floor. You might initially mistake it for sand or dirt, but it is actually a type of algae that can be difficult to identify and get rid of. It’s important to know whether swimming in a pool with mustard algae is safe or not, as well as how to address the issue if it arises in your own pool.

can you swim with mustard algae

While mustard algae, on its own, is not dangerous, it’s still not recommended to swim in a pool infested with it. The primary reason for concern is the potential for related bacterial growth when the algae is present. Ensuring that your pool’s chlorine levels are adequately maintained before taking a swim can help reduce any risks associated with mustard algae.

In this article, we’ll dive into the topic of mustard algae and its unique characteristics. We’ll also discuss how to properly clean your pool and take preventive measures to stop this pesky algae from making future appearances.

Understanding Mustard Algae

How to Tell if You Have Mustard Algae in Your Pool

Mustard algae, also known as yellow or gold algae, often appears as small, mustard-colored spots on the walls or floor of your swimming pool. It can sometimes be mistaken for dirt, pollen, or sand since it has a yellowish, yellow-green, or yellow-brown color. 

To determine if your pool has mustard algae, take a close look at the spots. If they easily brush off but return quickly, it is likely to be mustard algae.

Common Types of Pool Algae

There are several types of pool algae, including green, black, and mustard algae. Green algae is the most common and usually grows in pools with poor water circulation or low sanitizer levels. Black algae form dark, resilient spots that can be tough to get rid of. 

Mustard algae, as mentioned earlier, is a variant of green algae with a distinct color and tends to be more resistant to regular pool maintenance.

Why Mustard Algae is Hard to Get Rid Of

One reason mustard algae is highly resistant is that it can survive in chlorine levels where most other types of algae cannot. This means that even if your pool has adequate chlorine levels, mustard algae may still grow and thrive. 

Additionally, mustard algae can attach itself to pool toys, floats, and swimsuits, spreading from one pool to another. Proper cleaning of these items is essential to prevent the spread of mustard algae.

To tackle mustard algae, you need to be more aggressive in your approach: brushing the affected areas, keeping a higher chlorine level, and performing regular maintenance. While it can be challenging to remove, mustard algae can be managed and eradicated with consistent efforts and the right treatment methods.

Risks of Swimming in an Algae-Infected Pool

Bacterial Risk

Swimming in a pool tainted with mustard algae does not just affect the appearance and quality of your pool; it might also present a health risk. Mustard algae in itself isn’t inherently dangerous. However, a pool that supports the growth of mustard algae can also foster the proliferation of harmful bacteria, notably E. coli. 

When humans are exposed to E. coli, they can suffer from gastrointestinal issues, which manifest as symptoms like diarrhea, stomach cramps, and even fever. These conditions can range from mild discomfort to severe health risks, especially in children and the elderly. 

Effects on Swimmers

Diving into a pool with mustard algae might seem harmless at first, especially if you’re not immediately aware of its presence. But once in the water, swimmers might experience a series of discomforts. 

Skin can become itchy or irritated, and some individuals might develop rashes. But the effects don’t just stop at skin-level; prolonged exposure might lead to more severe health reactions. Some swimmers report feelings of nausea, while others might experience respiratory distress, especially if the algae are releasing toxins.

Spreading the Algae

The tenacity of mustard algae doesn’t just stop in the pool. When you swim in an algae-ridden pool, microscopic fragments of the algae can adhere to your skin, hair, and swimwear. If you subsequently enter a clean pool or a natural water body, these fragments can detach and start a new algae bloom in a previously unaffected location. 

Hence, it’s not just about the health of one pool, but potentially many others. To counteract this, swimmers should shower thoroughly after exiting an algae-affected pool and ensure that all swimming gear, including goggles and swimsuits, is cleaned properly.

Low Visibility

Beyond the health implications, mustard algae can present practical challenges for swimmers. A thick growth of algae can cloud the water, dramatically reducing visibility. This murky environment makes it tough for swimmers to spot potential underwater hazards, whether it’s a toy, a step, or even another swimmer. 

Reduced visibility can lead to unintentional collisions, which can result in bruises, cuts, or more severe injuries. If you’re unable to see clearly underwater due to an algae bloom, it’s a clear sign that swimming should be postponed until the pool is cleaned and the algae effectively treated.

Preventing and Treating Mustard Algae

Maintaining Water Chemistry

One of the key factors in preventing mustard algae is maintaining proper water chemistry in your swimming pool. You should regularly monitor the pH, total alkalinity, and chlorine levels of your pool water. Ideally, the pH level should be between 7.4 and 7.6, and total alkalinity between 100 and 150 parts per million (ppm) to create a balanced environment that is unfavorable for algae growth.

To maintain adequate chlorine levels, you may use a pool volume calculator to determine the appropriate amount of chlorine for your pool’s size. Regularly testing and adjust your pool’s chemistry levels will not only prevent algae growth but also ensure the water is safe for swimming.

Proper Filtration

Your pool’s filtration system plays a vital role in preventing mustard algae. A well-functioning filtration system removes contaminants like dirt, debris, and algae from your pool, keeping the water clear and healthy. 

Ensure your filtration systems are regularly maintained by checking for any clogs, cleaning or replacing the filter cartridges, and backwashing the sand or DE filters when necessary.

Moreover, running your pool’s pump for at least eight hours a day can help maintain water circulation and limit the growth of mustard algae. Remember to clean and disinfect all pool equipment regularly to avoid reintroducing algae into your pool.

Regular Pool Cleaning

Regular pool cleaning is essential in keeping mustard algae at bay. Incorporate a consistent pool maintenance routine that includes brushing the pool walls, steps, ladders, and other surfaces to remove any algae spores before they can develop. 

Vacuuming the pool floor and skimming the surface for floating debris will also help maintain a clean and algae-free pool environment.

In addition, you can apply algaecide and shock treatments to prevent mustard algae growth. However, it’s important not to overuse these treatments, as excessive amounts may negatively affect your pool’s water chemistry balance.

Using Pool Shock Treatment

One of the most common and potent solutions is pool shocking. Shocking a pool means drastically raising the chlorine levels for a short period to kill bacteria and algae. 

Using a calcium hypochlorite-based shock treatment is particularly effective against mustard algae. Products like “Yellow Out” are specifically formulated to target and eradicate this stubborn algae type. When using such products, always adhere to the guidelines mentioned on the label. 

Typically, after administering the shock treatment, it’s best to let it circulate and work its magic for about 24 hours. After this period, you should test the water to ensure the chlorine levels have returned to a safe range and the algae have been eradicated.

Maintaining Pool Equipment and Toys

An essential aspect of managing mustard algae is understanding that the pool water is just one part of the equation. Mustard algae are sneaky, and it can cling to virtually any surface that comes into contact with the contaminated water, from pool brushes to your favorite inflatable float. Hence, eliminating it from the pool water alone isn’t sufficient.

All pool equipment, toys, and even swimwear that might have been exposed to the algae should be meticulously cleaned. Using a diluted bleach solution or a specialized pool cleaning agent can be effective. 

Ensure you immerse or scrub every item, focusing on nooks and crannies where algae might hide. Additionally, the pool’s filtration system can harbor algae spores. Regularly backwashing the filter will ensure these spores are expelled, preventing a potential future outbreak.


Photo Credit: Richard J Kinch CC BY-SA 3.0