Real world truths about mustard algae in above ground pools

While reading other articles about yellow or mustard algae, I quickly realized that most who write about it, don’t really know or have much real-world knowledge of it.

As a pool guy for more than three decades, I have seen my share of yellow-colored algae in many different swimming pools. I have also battled with keeping it away and getting rid of it, mostly during my sixteen years of having a pool maintenance business.

Yellow-colored or mustard algae is common in above ground swimming pools. Although preventing its occasional growth can be almost impossible, getting rid of it is fairly easy if you use a sodium bromide product and strictly follow the directions.

ALL ALGAE ARE NOT CREATED EQUAL

Green algae are the most common growing algae in swimming pools. It usually means that there was a period when the pool had very low or no chlorine, which allowed a green algae bloom. Green algae are the easiest to keep from blooming and not too bad to get rid of depending on how much there is.

When talking about in-ground pools with cement finishes, the biggest algae enemy is black algae. Black algae is a nasty customer in that it grows roots within the pool surface, and then gets hard to completely kill.

Above ground pools don’t get much black algae if at all. This is because the vinyl isn’t porous enough for their roots to take hold. This is an advantage vinyl pools have over concrete ones. For above grounds then, their worse algae enemy becomes what’s next in line. And that is yellow algae.

THE CHARACTERISTICS OF YELLOW ALGAE

I don’t think it’s too important for a pool owner to have “Bill Nye the science guy” level knowledge on algae. If you want to know every scientific nuance about what grows in a swimming pool, then I’m afraid you’ll have to “google geek-out” elsewhere.

If you are taking care of a pool though and battling yellow algae, but not writing a paper on it, then read on. I will explain what you need to know about yellow or mustard algae and nothing more.

1 Yellow/mustard algae mainly grow on the walls of the pool

unlike green algae, yellow algae grow predominantly on a surface. It can exist suspended in the water, but you won’t see much of that. Oh and if you let it populate long enough, it’ll grow on the floor of the pool too.

2 Yellow/mustard algae doesn’t like direct sunlight much

In most cases with most pools, yellow algae will start growing and thrive better in areas of the pool’s wall that don’t get as much direct sunlight.

This is good to know if you are wanting to see it beginning to grow before it really takes hold. As a pool service guy, I liked to be able to identify the growth of yellow algae and treat for it before the paying homeowner could notice it.

3 Yellow/mustard algae form a coating that protects it from direct contact with any chlorine in the water

This is an important difference between it and green colored algae. This is also why just shocking the pool won’t kill it.

If you can grasp this concept of yellow algae having a protection from direct contact with chlorine, then it will be easy to understand how to kill it.

4 You can do everything chemically perfect with your pool and yellow algae will still periodically grow

Some pools won’t get too many blooms of yellow or mustard algae. Some pools will get it often and have to be treated for it every three weeks.

The occurrence of a yellow algae bloom can be lessened for some pools, but it’s almost impossible to never get it at all. So don’t beat yourself up too bad if you keep getting mustard/yellow algae. You may just have one of those pools that get it all the time no matter what.

WHEN YELLOW ALGAE BECAME MORE COMMON AND HOW I BATTLED IT

I’ve been in the swimming pool business for thirty-four years now and counting. My pool service business started in 1988 and finished completely in 2004.

In the first few years of me doing weekly maintenance for swimming pools, there were very few incidents of yellow or mustard algae. At first, I would just treat the yellow algae the same as green algae and could get rid of it fairly easily and it would stay away.

By the early nineties, I was seeing yellow algae much more often and it was coming back sooner and sooner. For the first few years of my service business, I only really used liquid chlorine and tablets as the sanitizer for pools. Real pool guys who know what they are doing rarely use any algaecides or clarifiers as they don’t help and are expensive.

The yellow algae bloom started getting so bad, that I had to start using a specialty chemical for it. The chemical was called “sodium bromide”, and it was a big deal to have to use it.

Jump ahead five more years, and every pool guy(at least in Central Florida) had to have sodium bromide on the pool truck at all times. Yellow algae blooms had become a very common occurrence and re-occurrence.

Over this transition from no yellow algae ever to yellow all the time, I did several experiments on pools trying to figure out why it was now happening and how to prevent it. This was important in that I didn’t want to do a bad job of servicing pools and wanted to keep the cost of chemicals down.

Over this period, I experimented with ph levels, chlorine levels, cyanuric acid levels, ammonia, No More Problems, more frequent brushing, and different filter cleaning schedules. I also documented weather patterns, pool usages, water temperatures, filtering and pumping conditions, and improved circulation.

In addition to investigating and documenting all of these variables, I talked with fellow pool service guys to get their experiences with battling yellow algae.

In those ten plus years of trying to figure out yellow algae, I made some conclusions. I concluded that yellow algae were here to stay and that no matter what you do, yellow algae can bloom. And it won’t be anyone’s fault.

Presently, yellow or mustard algae is a part of every pool guy’s ongoing battle with keeping swimming pools clear and free from algae blooms. It never went away.

THREE WAYS YOU CAN KILL YELLOW OR MUSTARD ALGAE

From my extensive experience with pool maintenance, there are three main ways to kill mustard or yellow algae. I’m sure there are some other more complex ways a lab using an ultra controlled environment can do it. But does knowing that really help you with your swimming pool? Yeah, no.

1 Use a product that has sodium bromide (recommended way)

These are products like Yellow Out, Mustard Knockout, Yellow Treat, and No More Problems.

If you’re not sure, check the ingredients of the product claiming to kill yellow algae. Its main ingredient should be sodium bromide. It’s important to follow the directions when using one of these products.

Sodium bromide works with chlorine(or some other sanitizer), requires brushing the entire pool, and running the filter system for a continuous 24 hours. I’ll explain later why these things have to happen in order for sodium bromide to work at killing yellow.

2 Aqua ammonia

A commercial-grade liquid ammonia is a nasty customer. It doesn’t play well with chlorine, hates the heat, and can knock you straight down if directly exposed to its fumes.

Are you scared yet? Well, I’m not really a fear monger, but when it comes to ammonia, you have to be very careful when using it.

Ammonia does a great job killing yellow algae though. And you don’t need to brush the pool either. All that you really need is to have a decent chlorine level in the water.

I don’t recommend a pool owner use commercial grade ammonia. As a pool guy, I experimented with using it, but most of the time chose sodium bromide instead to kill yellow. I would only use ammonia on some pools that would get yellow algae blooms very often. With those extreme cases, I would use ammonia occasionally instead of sodium bromide. Mixing up how I got rid of it would help keep the yellow at bay a little better.

3 Super, super chlorination

If you shock a swimming pool with enough chlorine, just about everything will die in the water.

As explained above, yellow algae have a protection against direct contact with chlorine, but if there’s a huge level of it in the water, then even that protective barrier cannot stop the chlorine from killing it.

I don’t recommend this method for killing yellow algae either. It takes waaaay too much chlorine to make this happen. Too much for any mere pool owner to want to pour into their pool. This should be left to not only a pool guy, but one with some years of experience under his/her belt.

Note: Most internet pool authorities(like troublefreepools) will disagree with this method. These are “internet only” authorities as they have no real-world experience. And that lack of experience shows often to real-world pool guys like me. Jus’ sayin’.

REGULAR POOL GUY’S EXPLANATION ON HOW SODIUM BROMIDE KILLS YELLOW ALGAE

Once again, if you want to geek out with a definition filled with chemistry jargon and equations, then I invite you to read elsewhere for that. I think uselesandsoonforgotteninformation.com has a whole section on this. Here, instead is my explanation:

In a nutshell, sodium bromide is like food for yellow algae. It sounds weird that you would want to feed something that you are trying to kill, but in this case, it’s necessary.

When you introduce sodium bromide into the pool, the yellow algae senses it as food. When it does this, it opens up to feed on it. Chlorine usually can’t penetrate yellow algae’s protective coating (so to speak), but when it opens in response to the presents of food(sodium bromide), then the chlorine can get in and kill it.

This is why you must shock the pool when applying a sodium bromide product (Yellow Out, Yellow Treat, etc.) There has to be a good amount of free available chlorine there to pounce on the yellow when it opens.

This is also why you brush the entire pool immediately after treating it with sodium bromide. The brushing helps to expose the yellow life attached to the walls to the chlorine.

The last thing that has to be done when treating a pool with sodium bromide is to run the filter system continuously for 24 hours. This is to keep both the sodium bromide (food) and the chlorine(killer) well circulated and present in every part of the pool. With this, the yellow algae everywhere in the pool will be exposed to the presents of food, and then the presence of the sanitizer(chlorine).

WHICH SODIUM BROMIDE PRODUCT IS BEST? YELLOW TREAT VS YELLOW OUT

Just like chlorine tablets, there are a lot of sodium chloride products that look different but are really the same. With a yellow/mustard algae algaecide product made to kill yellow, it’s all about the sodium bromide.

So, the only thing I check for is what percentage of the product is sodium bromide. That’s it.

Some products like Yellow Treat will be 99% sodium bromide, while others like Yellow Out will have only 82% sodium bromide. Usually, the product will less percentage of the active ingredient will be cheaper per ounce. With that, you can do some math to see how much actual sodium bromide you are getting for the money.

I prefer using products with the highest percentage of the active ingredient in it. I mean, if that’s what does the job, why put much of anything else in your product. Unless you are being deceiving in some way.

FOUR THINGS THAT CAN HELP PREVENT YELLOW ALGAE

As I said earlier, some pools will get yellow algae no matter what you do. There are some things that you can do to extend the times in between blooms though. I have done all of these things with good success.

1 Brush the pool weekly

For the first several years of servicing pools, I would brush the pool every week as part of the service. After a while, I stopped doing it every week because I determined that it was a waste of time to do it that often.

If your pool gets mustard/yellow algae a lot, then I recommend brushing the walls often. This will absolutely lessen the occurrence of algae blooms.

Above ground pool warning: When brushing a vinyl pool, be careful to use a brush made for vinyl pools only. Using an in-ground pool brush can cause damage to the liner.

2 Use “no more problems”

This is a product with sodium bromide in it and requires that you put some of it in the pool every week. If you read how sodium bromide kills yellow, then you can figure out why this product works to keep the algae away.

I remember when the “No More Problems” product came out. It was when yellow algae became a real problem maybe twenty-plus years ago. I, like most other pool guys, started using it with good success.

Within a couple of months though, I stopped using “No More Problems”. The Reason – I had to use way too much chlorine along with the product, which increased my cost. Using the product every week also would deplete my chlorine level in the pool, often leaving it dangerously low. “Dangerous” meaning that sometimes I would get a green algae bloom because the chlorine level would drop to zero long enough during the week for that to occur.

3 Cycle the chlorine level

It’s too lengthy to explain here, but you can’t just keep the chlorine level high all the time in a swimming pool. You must let the level go down to 1ppm or even less on a regular basis.

You do this to prevent a build-up of combined chlorine AND allow the value of shocking the pool to be high when you super chlorinate(shock) the pool.

Shocking the pool when its chlorine level is low is very helpful in preventing yellow algae blooming.

4 Good circulation

Good pool water circulation does a lot of good things. Making it harder for yellow algae to grow is one of them. With above ground pools, this isn’t as much of an issue as their shapes are simpler.

For above grounds, you can improve your circulation easily by pointing the return jet toward the pool’s wall. This will create a whirlpool effect in round pools and much better circulation in oval-shaped ones.