How To Treat Mustard Algae In Your Pool

Mustard algae can be a pesky invader, turning your sparkling pool into a murky mess. Unlike other types of algae, mustard algae are known for their resilience and can quickly spread if not treated properly. This type of algae typically appears as a yellow or mustard-coloured growth, often clinging to the walls and floor of the pool. Some people confuse mustard algae with sand or dirt in the bottom of the pool, so it’s important to be vigilant in identifying and treating it.  

Recognising mustard algae early is crucial. Unlike green algae, which floats and turns the water cloudy, mustard algae tends to cling stubbornly to surfaces and can be brushed off easily only to settle back down again. It usually forms in shady areas of the pool and can survive even in well-chlorinated water. The resilience of mustard algae means it can often be found clinging to pool toys, floats, and even swimsuits, leading to recurring infestations if not thoroughly eradicated. 

Is Mustard Algae Harmful?

Mustard algae (or yellow algae), while not directly harmful to humans, can create an unpleasant swimming environment and potentially harbour harmful bacteria. These algae are particularly resistant to chlorine and can cling to pool surfaces, toys, and equipment. If left untreated, they can lead to increased pool maintenance costs and reduce the overall enjoyment of your pool. 

10-Step Mustard Algae Treatment Process

Follow these ten steps to effectively eliminate mustard algae from your pool: 

1. Super-Chlorinate Your Pool

• For pools between 20,000 to 30,000 litres, add 1 kg of stabilised chlorine.

• For pools between 30,000 to 45,000 litres, add 1.5 kg of stabilised chlorine.

• For pools between 50,000 to 65,000 litres, add 2 kg of stabilised chlorine.

• Alternatively, use liquid chlorine as required.

2. Balance the pH Levels

• Ensure your pool’s pH level is at 8.2 ppm or higher for optimal algae treatment.

3. Prepare the Pool Equipment

• Disconnect the suction cleaner and remove the plate from the skimmer, but leave the cleaner and any robotic devices in the pool to be treated.

4. Brush Pool Surfaces

• With the pool equipment running, brush all walls and the floor of the pool to stir up the algae and make it easier for chemicals to work.

5. Add Algaecide

• Add 1 litre of Focus Powercide Algaecide and 1 litre of Focus Hydroclear Algaecide.

• Alternatively, use 2.5 litres of Tropical Algaecide or the amount specified on the product label based on your pool size.

6. Treat Pool Accessories

• Wash down pool edges, toys, chairs, and any other items that have come into contact with algae spores. Leave these items in the pool during the treatment process to ensure they are thoroughly cleaned.

7. Add Clarifier

• Add clarifier to a bucket of water and distribute it evenly across the pool, then brush the pool well again.

• Use Ultrasheen clarifier for sand filters and Bling clarifier for cartridge filters.

8. Run and Stop Equipment

• Keep the pool equipment running for a minimum of 4 hours after adding the chemicals.

• If you have a media filter, set it to recirculate. For cartridge filters, remove the cartridge.

• Turn off all equipment, preferably overnight, to allow sediment to settle.

9. Vacuum Algae Residue

• Vacuum the algae residue to waste, ensuring there is enough water in the pool.

10. Final Cleaning and Equipment Reset

• Perform a general vacuum if needed to clean up any remaining debris.

• Backwash and rinse the filter as required, and clean the cartridge element if you have a cartridge filter.

• Return all pool equipment to their regular timers.

• After 5-7 days, perform a water test to re-balance the pool’s chemistry.

How to Prevent Mustard Algae from growing

To prevent mustard algae from returning, regular pool maintenance is key. Here are some tips: 

• Maintain Proper Chlorine Levels: Keep your chlorine levels consistent to prevent algae growth.

• Regular Brushing: Brush the pool surfaces weekly to remove any potential algae spores.

• Keep Your Pool clean: Regular cleaning will help you combat this and many other types of algae, such as black spot algae.

• Clean Pool Equipment: Regularly clean pool toys, accessories, and equipment.

• Monitor pH Levels: Keep your pool’s pH levels balanced to ensure a healthy swimming environment.

• Use Algaecide: Consider adding an algaecide to your regular pool maintenance routine to prevent algae buildup.

By following these steps and preventative measures, you can keep mustard algae at bay and enjoy a pristine, inviting pool. Don’t forget to scrub and disinfect all of your pool toys and floats and machine wash your swimmers. Mustard algae can live outside of your pool so taking these steps will help make sure you don’t reintroduce the algae back into your pool! At Master Pool Care, we’re dedicated to helping you maintain a beautiful, healthy pool year-round.