Algaecides for pools and spas are used to help you get rid of algae, small plant-like organisms which grow in the water. Of the 3 most common types, green, yellow (mustard) and black, you will most often find green algae in your pools and spas.

According to Rivers Pools and Spas, the main reason why algae grow in your pools and spas is because they haven’t been properly treated with a sanitizing chemical. If you take no steps, you’ll soon find algae free floating in large numbers, which can cause your entire swimming pool or spa to turn green. To avoid this, we’ll help you find the best algaecide in the market. Prior to their application and in really bad cases, algae must be vacuumed directly out of the pool.

Without further ado, here’s our algaecides lineup for you to consider!

Best Algaecide Comparison

1. GLB Pool & Spa Products 71114 1


  • Great for mustard algae
  • Lasts all pool season
  • Compatible with other pool chemicals

2. Kem-Tek KTK-50-0006 Pool and Spa 


  • Long lasting algaecide
  • Safe with all pool and filter types
  • Non- foaming algaecide

3. PoolRx Algaecide Unit, 7500 to 20000 gallons


  • Eliminates all types of algae
  • Effective for up to 6 months
  • Also Ideal for Salt Pools

Buying Guide

When buying pool algaecides, you need to have several important things in mind such as, how effective the pool algaecide is, whether it is safe for swimming pool users and whether it leaves any damage or stains on your pool or spa.

All of you who have fought up an algae bloom will probably agree that lots of time, money and effort can be saved by carefully balancing your water and adding a weekly dose of your best algaecide for swimming pools to prevent algae.

Under the hot summer sun and due to the inconsistencies in a swimming pool’s sanitizer levels, different types of algae appear to ruin the summer.

Algae are single-celled plant forms which, although microscopic in size, multiply to virtually millions before they become noticed. By that time, it’s usually too late as they are highly resistant. Therefore, in most cases prevention is the cure. To start off, make sure to use these top notch digital pool water testers to make sure the pH is good.

Various types of algae exist in a wide variety of colors but the next few are the most common in pools.

Green Algae

The most common form of algae in swimming pools, green algae, vary in color from blue-green to yellow-green to dark-green. They can be free floating or wall-clinging.

A solid amount of pool algaecide with some brushing and shocking does the trick. You need proper pH levels and chlorine treatment after brushing. Then shock your swimming pool to raise the chlorine level to above 3 ppm. Add a proper dose of  pool algaecide and monitor filtration to ensure proper water flow. If needed, repeat the process. 

Black Algae

Black types of algae (more of a blue-green in color) form in crevices and cracks of your pool surfaces. Black algae are often found in concrete or plaster finished swimming pools because of their rough surfaces.

They form a layer of slime which makes them resistant to the usual chlorine levels. Black types of algae doesn’t change water color but make ugly dark spots on the pool surfaces.

Thorough brushing is a must as a way to break the slime layer open. No brushing – no successful treatment. Shock the pool and use a swimming pool brush again before adding algaecide test your pool water.

Mustard Algae

Mustard or yellow algae are chlorine-resistant forms of green algae. They look like dirt but they are much worse than that. They should be treated the same as black algae.

Brush the algae off the walls first and then vacuum your pool.

Make sure to choose the right pool algaecide for the type of algae you have or want to prevent and do follow the initial and weekly pool maintenance dosage to protect your pool from stains, foaming and damages.

Metallic (longlife) pool algaecides

These are usually copper based because copper is toxic for algae as it disrupts their photosynthesis process. The higher percentage of copper, the more effective the  pool algaecide is.

Following the dosing instructions carefully is a must in order to avoid blue-green or black stains and damage to your plaster and metal parts. For safety reasons you have to wait for a certain time (as recommended in the instructions) before swimming. Otherwise the higher dosages might affect your hair or cause skin or eye irritation.

Non-metallic (regular) pool algaecides

These are either a polymer (“poly”) or quaternary ammonium compound (“quats”), or their combination – “poly-quats”. They disrupt cell membranes of algae and thus help chlorine to kill them. They also lower the surface tension of water and “wet” the algae cell walls. This wetting helps stop algae from sticking together and prevent further algae spreading.

If you don’t follow the proper dosing, quats may cause unpleasant chemical smell and foaming. Quats usually provide safe swimming environment immediately if you stick to the instructions provided.

What are the Best Pool Algaecides on the Market?

1. GLB Pool & Spa Products 71114 1- Quart Strike Out

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GLB Strike Out, a top algaecide, is a triple, chelated 7.4% copper algaecide for swimming pools which eliminates green and yellow algae. Being concentrated, it’s economical and should be diluted with at least nine parts of water. Don’t forget to shock your pool as well.

Apply under sunny conditions for most effective results and you can enjoy a swim immediately. GLB Strike Out leaves no stains so it’s safe to use in all kinds of swimming pools including salt water if you follow the instructions provided.

It’s compatible with chlorine, bromine and ozone sanitizers. You’ll get most effective results if you apply it in sunny weather. Don’t forget to sprinkle the solution around all the edges of your swimming pool.

For swimming pools between 17000-25000 gallons algae disappear completely in anything from overnight to a week, depending on chlorine levels, how balanced the water is and how much the algae have spread. Brushing and vacuuming swimming pools afterwards made the swimming pools look beautiful and the water crystal clear.

GLB Strike Out really does kill and prevent yellow algae from coming back and performs best when used regularly throughout the season. GLB being concentrated and assuming you keep your swimming pool balanced and chlorine levels up, one bottle will last the whole summer.

If you intend to use it in your spas, be aware that it’s the milliliters of GLB Strike Out that would do the job without making your water too blue in color. Ask for the recommended quantity based on the volume of your spa and you won’t go wrong.

For the price, GLB Strike Out is one of the best pool algaecides in the market and does the job as expected without stains or damages to your swimming pool plaster or metal parts: people love it and algae surely hate it!

Things We Liked

  • Great for mustard algae
  • Lasts all pool season
  • Compatible with other pool chemicals
  • Great value for money

Things We Didn’t Like

  • Could use better instructions



2. Kem-Tek KTK-50-0006 Pool and Spa 60-Percent Concentrated Algaecide, 1 Quart

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Kem-tek Concentrated Algaecide is a reliable pool and spa non-foaming polymer algaecide. Safe with all pool and filter types, it will last long and keep your pool clear and algae-free for a long time.

Kem-Tek Concentrated Algaecide will stay active in your pool, with minimal loss of effectiveness due to water temperature,sunlight or swimming use. As Algae usually starta in difficult-to-reach crevices in the pool surface or areas with poor circulation, it is best to apply it first at the beginning of a season.

It will be much easier to maintain your pool afterwards and your pool water will never get to look murky.

The middle of the swimming season is prime time for algae to develop. This is because algae grows with the rise of the temperature. This concentrate will prevent the formation of algae and their re-growth without any damage to your pool.

Available in 32-ounce size, Kem-Tek 60% Concentrate is probably the strongest polymer algaecide available for pool use. 100% soluble in water and with zero evaporation, it has a very mild odor but it’s really potent as regards its algaecide efficiency. Handle it carefully as it’s irritable for your eyes and skin so safety goggles and gloves are recommended.

It also activates using chlorine so shock your pool first. After that, your pool maintenance will be cheap and really simple as long as you keep the water balanced. If your pool is blooming with mustard algae, you might consider using a copper-based algaecide first and then Kem-Tek 60% Concentrate for further protection and prevention.

Things We Liked

  • Super concentrated and powerful
  • No stains or damage to pool
  • Good algaecide for the money

Things We Didn’t Like

  • Not great with mustard algae



3. PoolRx Algaecide Unit, 7500 to 20000 gallons

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PoolRx Algaecide is a unique chelated mineral algaecide and chemical reducer. Clean your filter first, then, drop the PoolRx unit into the pump basket or skimmer. Add the right dose based on the volume of your pool and in a couple of days you will have crystal clear water again.

The proprietary blend of minerals immediately dissolves and is effective for up to six months. Using PoolRx greatly simplifies pool and spa maintenance by eliminating algae while freeing up low levels of chlorine so they are more active in the water. It needs as little as 0.5-1.0ppm of chlorine.

Since 1994 PoolRx has been proven as one of the best algaecide for pools.It’s ideal solution for all chlorine pools, salt pools and spas. It will reduce your chlorine or salt chlorine demands by 50% and you won’t ever need phosphate removers, sodium bromide, and clarifiers and save you a nice chunk of money and a lot of time.

PoolRx also reduces energy consumption because you will be able to cut down on circulation pump run time thus saving money on your electricity bill. Not to be overlooked when shopping for best algaecide for pools.

PoolRx minerals include a natural descaler. This will help to extend equipment and surface life. Less wear and tear goes without saying. Less chlorine means 50% less cyanuric acid build up so water quality will be better with less frequent draining and refilling your pool.

Things We Liked

  • Easy to use and efficient
  • Eco-friendly with relatively few chemicals
  • Hands off application
  • Reliable and safe to swim with

Things We Didn’t Like

  • Doesn’t always last as long as advertised
  • Can clog smaller pool filters



4. In The Swim Super Pool Algaecide – 1 Quart

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In The Swim Super Pool Algaecide is another copper-based algaecide which efficiently kills and prevents re-growth of green and yellow algae. Super-concentrated and with non-foaming properties it will make your pool look super cool!

In The Swim Super Pool is another copper-based algaecide which efficiently kills and prevents re-growth of green and yellow algae. Super-concentrated and with non-foaming properties it will make your pool look super cool!

As it contains 7.1% chelated copper, Super Pool will deal with most algae. It’s a deadly weapon against green and mustard algae but it does not help with black ones.

If you plan to include this algaecide into a routine schedule of maintenance, one bottle should do for the seasonal opening and 5-6 rounds of maintenance. Make sure to monitor chlorine levels after use as Super Pool works in synergy with chlorine.

The initial dosage is 4 ounces per 10.000 gallons and maintenance dosage is 2 ounces and shortly after treatment you’ll be able to enjoy a perfect swim. Yes, it is safe to swim directly after use!

Affordable, concentrated and reliable, Super Pool will not disappoint as long as you stick to recommended dosage and keep your chlorine levels up.

Super Pool is not recommended for use with well water.

Things We Liked

  • Solution acts fast
  • No foam
  • Safe to swim after use

Things We Didn’t Like

  • Not effective for black algae



5. SeaKlear 90-Day Algae Prevention & Remover, 1 Qt

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SeaKlear Algae Prevention & Removerhas 11.8% copper sulfate pentahydrate as active ingredient and a powerful ally against blue-green, green, mustard and black algae.

As long as you follow the instructions and in balanced pool water, you will get no algae for 3 months. The same goes for saltwater pools but it takes a bit more time for the algae to clear out.

16 fluid ounces is enough for 10000-gallon pools and for severe algae treatment best use double dosage of 32 fluid ounces.

SeaKlear Algae Prevention & Remover is non-staining, non-foaming and as long as you keep your water reasonably balanced you will have great results with all algae. Mind you, it’s advised to brush and vacuum the pool beforehand.

Although blue in color, it will not color or discolor your steps or other pool parts, which is great. What it will do is help you battle out with algae as long as you look after your pool properly and do not let it grow into a green pond before actually start thinking of using algaecide.

Things We Liked

  • Effective for all algae
  • No foam, no stains
  • Gentle on the skin

Things We Didn’t Like

  • Doesn’t always work for full 3 months
  • Not great with major algae spread



6. McGrayel Algatec 10064 Super Algaecide for Green, Yellow and Black Algae, 64-Ounce

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McGrayel Algatec has a biostatic inhibitor function which effectively fights algae and provides superior cleanup of your pool. It works well with all types of chlorine and non-chlorine based sanitizers.

With McGrayel Algatec, eradicating both yellow and black algae has never been much of a challenge due to its highly effective dual-action properties. This algaecide will also sanitize your pool and make the water look sparkling and clear.

It kills most algae in 8-24 hours and it takes it about a week to eradicate black algae. It is also salt pool friendly and contains no metals, bromides, or quats. Without interfering with pH levels Algatec enables you to have a swim right after treatment.

Depending on how much algae there are, you will need 1-4 cups per 20,000 gallons of pool water. Black algae being so stubborn, you might need to take additional measures.

By most users it’s great for black algae so just make sure you start off on time, follow the instructions and enjoy the welcomed change of your pool. Some users might have started late or simply expected more for the price.

Things We Liked

  • Great for black algae
  • works well with chlorine

Things We Didn’t Like

  • Not as powerful as one would hope 
  • Not great w/ all types of algae