The Best Tips for Choosing the Best Algaecide for Your Pool

If you need tips for choosing the right algaecides for your pool, this article will walk you through the basics of your pool and give you tips to help choose a quality algaecide.

Algae is unsightly and can create a hazardous environment in your pool – that’s why we wrote this buying guide on how to choose the best algaecide.

Algaecide: Pool with Algae

Read on to find out everything you could ever want to know about how to select a good algaecide for your pool. From which type might be suitable for you, whether or not you need one or two bottles, to what chemicals are in them – we cover all the bases. Enjoy!

What Is Pool Algaecide?

When a pool is not adequately treated for algae, the pool can result in an unsightly appearance. Algaecides work to kill the algae by making it unfit for survival and denatures proteins that allow the algae to grow.

Algaecides are products found in every type of pool and spas, such as those which utilize chlorine or bromine as a disinfectant.

While shocking your pool with chlorine is the most effective method to cure most algae problems, pool algaecide is used as a preventive measure to keep the algae from recurring in the future.

Pool care should involve using an algaecide regularly, mainly when you’re opening or closing your pool for the season.

How Does Algaecide Works?

Algaecide is an organic compound that is sprinkled into the water of a pool with the intent of killing algae. It comes in many different forms and has been developed for various pools.

However, because it only kills certain forms of algae, there is confusion for how it works. One reason for this confusion may have to do with the rate that algaecide degrades in different water compositions.

There are also natural reasons that algaecide may work better or worse depending on certain temperatures and pH levels. Although there’s a lack of research on how algaecide works, they usually interfere with algal cell division or prevent the creation of new cell proteins, which are essential for cell survival.

Algaecide Can Help Eliminate These Three Kinds of Algae

Lately, we have been introduced to the idea that our swimming pool is not just a great escape from the sun, but it can also be an amazing natural resource. The water holds a wide variety of potential benefits, including keeping your skin and hair well-moisturized and healthy.

However, like all forms of life living in ecosystems, there is always a trade-off. One such trade-off is algae, sometimes referred to as “slime” or “green scum.” These are generally three types of algae that can be found most often in pools: 

Green Algae

Algaecide: Green Algae

Green algae are single-celled organisms that live in colonies on the surfaces of clean water. The colonies can also grow on the sides of pools and at any time on decking and other pool surfaces. It is usually greenish and tends to have a gloomy appearance, but it can also be dark green or grey.

While the growth rate is slow for this type of algae, it’s still one of the most common types found floating around your swimming pool water

Black Algae

Black Algae

Black algae are not algae at all, but rather a fresh water-born fungus. It usually has a slimy and black appearance in the water.

The growth rate for this type of algae is speedy and can be seen developing within days, or sometimes even hours. These parasites are more common during the summer months, where they can spread rapidly.

Mustard Algae 

Mustard algae are also sometimes known as blue-green algae caused by cyanobacteria. This particular type of bacteria only needs sunlight to grow on its colonies, making it ideal for warmer climates like pools in Arizona and Florida.

A noticeable feature of this type of algae is that it will have an intense color that ranges from dark green to yellowish.

Pink Slime

Pink slime is often mistakenly referred to as “red” or “pink algae.” Although it is not an algae in the traditional sense, it spread fast, is chlorine resistant, and doesn’t need sunshine to thrive. 

What Are Types of Pool Algaecide Can You Buy?

There are three different types of pool algaecides that you can buy: Quat Pool Algaecides, Polymer/Polyquat Pool Algaecides, Metallic Pool Algaecides, and Sodium Bromide.

Quat Pool Algaecides

Quat pool algaecides are technically a kind of detergent used to destroy most varieties of stubborn algae in your swimming pool.

Typically, these are the most affordable price algaecide, and they are available in concentrations of 10 percent and 50 percent. While excessive usage of this kind may create foaming (since it is essentially soap), unlike metallic algaecides, there is no danger of coloring your pool.

Quat Pool Algaecides contain no chlorine and will not damage vinyl-liner pools or metals in metal pools. However, the disadvantage to using this type of algaecide is that it can be slow and ineffective in highly chlorinated water.

Polymer/Polyquat Pool

Polymer/polyquat algaecides are a variation of the Quat compound. They offer two unique benefits over other algaecide formulations. They are non-staining and non-foaming algaecide.

Working similarly to quat algaecides, the polymers bind rapidly to the negatively charged algal cells, spreading across the bloom and smothering algae growth.

On the other hand, it is twice as effective and twice as long-lasting as Quat algaecide, but it is also the most costly algaecide version on the market. These are available in concentrations of 30 percent and 60 percent.

Metallic Pool Algaecides

Metallic algaecides work by targeting the outer cell walls of algal cells, poisoning the nucleus of each algae cell, to exterminate an infestation.

Metallic-based algaecides have been made to offer a streamlined and long-lasting product. In addition, they are effective against a broad range of organisms and are entirely natural.

These pool algaecides are available in concentrations of 45 percent, 60 percent, 100 percent, or 160 percent. 

If you’re dealing with a black algae infestation, silver algaecides are a cost-effective way to eliminate these tough algae blooms from your pool.

Sodium Bromide

Sodium bromide (NaBr) is a chemical compound that is made of sodium ions and bromide ions. It can be created by mixing or dissolving sodium chloride (NaCl) in water.

If you want to use it in your pool, it’s best to add it after the pool has been opened for the season, which will also help prevent corrosion. It usually comes to a concentration of between 50%-150%.

While not explicitly classed as an algaecide, Sodium Bromide is an excellent method to prevent and destroy algae growth in your swimming pool.

The only drawback is that this reaction will cause your free chlorine levels to decrease, so you will need to monitor the balance of chemicals in your pool while doing this procedure.

What’s the Best Algaecide to Use?

The best algaecide for your swimming pool would depend on the kind of algae that you’re trying to control in your pool.

Here are several points to look at when deciding which type of algaecide will work best for you:

  • If you have an iron stain in your swimming pool, it would be better to use Quat algaecides. However, be mindful not to add too many Quat algaecides because they can create a foamy mess in your pool.
  • For small amounts of algae, it is recommended to use Polymer or Metallic based compound. However, it is mandatory to keep in mind that metallic algaecides can lead stains to your pool.
  • If you need a cost-effective solution, then sodium bromide may be suitable for you. 

Though in my opinion, a polyquat algaecide is the best solution to use to keep algal at bay since it does not froth up or discolor your pool liner and walls, which is a significant concern with other products.

Can You Swim After Treating Your Pool With Algaecides?

What about swimming right after treating your pool? The answer to this question depends on the type of algaecide that you are using. If you are using quat algaecide, it is best to wait 24 hours before jumping into the pool for a swim.

On the other hand, if you’re using polymer or metallic-based compounds, you need to monitor your pool’s chlorine and ph levels to see if it is appropriate for swimming. 

What do I mean by monitoring these levels? Two main things will help determine if a pool has been treated with an algaecide and is safe for swimming – these are chlorine levels and PH levels.

How Long Do Algaecides Last?

If you already have an algaecide in your pool, then the length of time it will last depending on the type of algaecide you are using. For example, if you are using Polymer-based or Metallic based compounds, then it would last anywhere between 7-10 days.

Quat algaecides will likely last about three weeks once they are in the water because of their efficiency at preventing algae growth as well as killing them off more quickly. Some algaecides provide protection for 90 days, while others may provide protection for up to 6 months when used in your water.

Whatever method you choose, keeping algae at bay takes a constant effort, and it should be a regular component of your pool’s overall maintenance schedule.

What’s the Best Way to Store This Stuff?

Quat algaecides can be effectively stored by transferring them into a container such as a metal canister with a tight-fitting lid for long-term storage.

Polymer-based and Metallic based algaecides should be stored in a container away from other chemicals that may react to the product. These products should also be placed in a cool, dark area with no direct sunlight and water exposure.

How Much Does Algaecides Cost?

Pool algaecides don’t cost that much, but since you will use them regularly to treat your water quality, they will represent an ongoing expense to maintain your pool algae-free.

Different algaecides vary in what they cost. For example, quats are usually the least costly, followed by metallic algaecide, with polymer algaecide being the most expensive.

The goal is to select an algaecide that is effective while also considering the expense of how many times you will be using it to your pool. 

When Should You Add Algaecide to Your Pool?

Algaecides should be used before the algae can grow, as they are less effective on algae that are already in the pool. You should not wait until your pool water is green before adding algaecide, as it will likely not be effective.

You need to monitor your swimming pool and add algaecide as needed regularly. Since you cannot see chlorine or other chemicals in the water, you have to do routine checks of your swimming pool chemistry using a test kit. If you suspect that the chemical balance is off, then add more chlorine or acid accordingly.

Here are some other circumstances that you should consider when adding pool algaecides:

  • You can add algaecides before closing your pool for winter.
  • You should also add algaecides when opening your pool in summer or spring.
  • Some pool owners like to apply algaecide to their pools and spas in warm weather since pool algal thrives in the sun.
  • Some individuals weekly dose their swimming pools with algaecide as part of their pool care routine.

Editors choice/tip: To get the greatest results, use the pool algaecide while the sun is shining. Algae and organisms grow when the sun is out and shining. 

Can You Do Shock Treatment and Put Algaecide in Your Pool at the Same Time?

The answer is that it depends. If the water is cloudy, then shocking the pool first should clear up the water making it easier to add algaecide. However, if you already have green pools, you will likely need to pool shock before adding the algaecide treatment.

Also, you should not pool shock and then apply the algaecide simultaneously since the two become useless when combined.

We recommend that you shock your pool and then apply the algaecide when the chlorine level reaches 5 PPM.


Keeping green algae, yellow algae, blue-green algae, and black algae out of your pool or spa may be a daily struggle. However, with the best pool algaecide, you have a huge chance of winning.

Adding these swimming pool chemicals during routine pool care is probably the most effective method to deal with the annoyance of algae growth.

These articles provide tips and tricks for maintaining a healthy swimming pool.

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About the author

Brian Anderson

The rather dry pool world out there is in need of some passion to make it shine. With the help of my son Ruben and his wife Maria our mission is to help you create the favorite spot of your house - your pool.

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