Mustard algae, also referred to as yellow algae, can be a very frustrating pool issue. When you first spot signs of mustard algae in the pool, you may choose to believe you see sand, dirt, or a stain in your pool. Once you get through the denial period, it’s best to act as quickly as possible to treat the issue and get your pool back to being swimmable.
Check out this helpful information that every pool owner should have about mustard algae.
What Is Mustard Algae?
Mustard algae is a microbe that likes to stick to the side of your pool and lots of other pool-related equipment. Yellow mustard algae will be on the bottom of the pool, the equipment, toys, and even your bathing suit. Unlike green algae that will disappear with chlorine, the mustard algae is chlorine resistant and will give you a bit more trouble with removal.
Some people struggle with how to spot and prevent mustard algae. It can look like a stain or dirt in your pool at times. It is not the same bright green color that you are used to seeing when it comes to algae. One thing you will notice about mustard algae is that it will brush off, but it returns, and it will eventually turn your entire pool a terrible green color.
Why Is Mustard Algae Bad for Your Pool?
Mustard algae stick to the walls and the sides of your pool. When it sits for too long, it can create stains, especially if your pool has a vinyl liner. In addition to potential stains, mustard algae will cause more bacteria growth in your pool if left alone. The more bacteria in the pool, the bigger a problem you have on your hand.
Mustard algae is not all that harmful or dangerous to humans, but when bacteria start to grow because of the algae, it can then be dangerous.
Causes of Mustard Algae in Pool
There are a few main reasons that people get yellow algae in their pool. If you can determine why you have mustard algae pool, it makes it much easier to prevent the issue in the future.
- Balance Chemicals: Anytime your pool chemicals are out of balance, you open the doors to a wide range of pool issues; you need to monitor your pool chemicals every few days and, at the very least, once a week.
- Filter Not Running Enough: We get it; running a pool filter can be a real ugly addition to the electric bill. However, once it gets warm outside, you will see algae start to grow if you are not running the filter enough. The more you keep the water moving, the easier it is to keep mustard algae away. Run for at least 8-12 hours a day.
- Shock the Pool: When was the last time you shocked your swimming-pool? You should be shocking the pool about once a week, especially during prime season.
- Watch Out for the Transfer: Have you been to the beach, swam in a friend’s pool? You may have transferred algae or bacteria back to your own swimming pool water.
Get Rid of Mustard Algae in 9 Fast Steps
Proper pool maintenance and learning how to remove stubborn mustard algae isn’t difficult. However, removing mustard algae isn’t as easy as leaving your pool pump running 24 hours a day.
Be sure to pay close attention to which pool chemical you’re using during your pool cleaning process. Pool safety will be greatly impacted if you use too much liquid chlorine, or put too many chlorine tablets in at once.
Let’s dive into proper pool care and water chemistry and work on making your pool cleaner.
1. Clean All the Gear
As we mentioned, the mustard algae in your pool is probably not just in your pool. Chances are the algae is also on your pool equipment, your bathing suit, the pool toys, and anything else even remotely close to the pool. If you are going to spend the time to get the algae out of the pool this equipment needs to be cleaned as well.
Using regular Clorox on your removable ladder, solar blanket, diving-board, swim goggle, float toys, and other pool accessories that come in contact with the water is fine. After you disinfect, be sure to rinse them off appropriately to prevent staining.
Use color safe bleach (diluted with water) to sensitive objects. If you can use a laundry detergent with a small amount of bleach to clean bathing suits and towels, that is a good idea as well. This is also an excellent time to take all pool equipment like brushes and hoses and put it in your pool’s low end.
2. Brush the Pool
This is a step that you are going to have to get used to. Unfortunately, there is a lot of brushing involved when you need to get rid of mustard algae in a pool. You will want to scrub the sides, the steps, and even the pool ladders as well. Most of the time, you will see algae on the bottom of the pool, and make sure you scrub that as well. Even if there are areas where you can’t see mustard algae brush it anyway.
- Pool wall brush for cleaning gunite pools with hard-surface finish
- Combination of durable nylon and stainless steel bristles for extra strength
- Pool brush features an 18-inch die-cast aluminum back and handle
3. Vacuum the Mustard Algae in the Pool
Once you have finished brushing the pool, it’s time to take out the pool vacuum and use that to clean any additional algae that the brush did not remove. Ensure that when you have completed vacuuming that you leave the vacuum parts in the low end with the rest of the pool gear.
4. Fill and Test
If your pool needs any water, now is the time to add it. You are trying to get your pool to a baseline level that you can then work on to try and clear up. This is an excellent time to test your pool and see what the situation is with both chlorine and pH level. This is going to be your starting point, and all other tests will be based on these numbers and trying to get things back to the proper levels.
- Features a photometer which gives you a digital reading of test results.
- Water resistant housing and carrying case provided.
- Tests Free Chlorine, Total Chlorine, Bromine, PH, Alkalinity, Calcium Hardness, and Cyanuric Acid.
- Uses liquid reagents for all test factors except Cyanuric Acid, which uses tablets.
One dose of shock is not going to cut it for mustard algae in a pool. It is unfortunate, but you will have to spend a fair amount of money on triple shocking the pool to eliminate this algae. Where a standard chlorine shock is one pound for every 10,000 gallons, with mustard algae removal, you need three pounds for every 10,000 gallons.
It is always a good idea to shock your pool at night. The sun tends to burn off the shock very quickly when it is added earlier in the day. The treatment will not be quite as effective, and you may end up having to go through this process again.
When you triple shock the pool like this, keep the pool filters running for twenty-four hours. The movement will help clean the water and the sides and bottom of your pool and make it harder for the mustard algae to grow.
6. Brush (Again)
Once the pool has been shocked, you will need to spend the next forty-eight hours brushing your pool as much as you can. The brushing helps keep the yellow or mustard algae suspended in the water. When the algae are in the water, the shock can do a much better job of treating it. You will also help to make sure that the algae have no time to even think about growing. Don’t let that yellow dust settle!
7. Adjust Chemicals
Now is the time to test your pool chemicals again. Adjust to get the levels to the point that they should be and then move to the next step.
Yes, you need to shock one more time. By now, you probably think this is an excessive amount of pool shock. The problem is, mustard algae is persistent, and it will continue to come back. Trust us; you don’t want to go through this process again. For this shock treatment, you can just do the traditional one pound of shock for 10,000 gallons.
9. Test and Adjust Chemicals
The last step is to test the pool chemicals yet again and adjust as needed. Make sure that you get your pool back to normal and then start checking on things more often. Test the water every few days or at least once a week.
How to Prevent Yellow Algae Moving Forward
If you want to prevent pool algae moving forward, there are some essential steps that you should take. Some people like to put an algaecide in their pool as a weekly treatment to help discourage algae from growing. Although this can be helpful, it’s not necessary. If you follow the advice we are about to give, you should not have to deal with mustard algae in your pool ever again.
- Check your pool chemicals all the time!
- Adjust chemicals at the first sign of any issues.
- Brush your pool often and clean pool equipment and toys with a bleach and water solution.
- Don’t get stingy on those filter running times; you need 8 to 12 hours day when you are in season.
- Learn to recognize mustard algae right from the start; the quicker you attack it, the better your chances are of getting rid of it.
- Shock your pool at least once a week when the weather is warm and sunny; this will work as a great preventative measure.
The best way to keep your pool free from mustard algae is to pay attention to it!
Finally No More Algae on the Bottom of Your Pool
Hopefully, our guide giving you the best way to get rid of mustard algae in a pool has helped you feel like there is an end in sight. A battle with algae can ruin a good part of your summer swimming season. Knowing how to spot mustard algae, how to kill mustard algae, and how to prevent it will go a long way in making sure you never have to deal with this issue again.
For over 15 years, Sean Moore has been sharing his love and enthusiasm for swimming pools and hot tubs with everyone he knows. His goal is to help everyday people DIY their maintenance to save money by teaching how to properly take care of your equipment, safely and correctly balance chemicals, and extend the life of your water oasis.
Pricing on this page was last updated on 2022-10-01