How to Get Rid of Pool Algae

Pool algae is a common hurdle for many pool owners. These aquatic plants can give your pool a discolored green, yellow, or even black appearance and cause unsafe swimming conditions. In this blog, we'll explore the various types of pool algae, effective removal strategies, and proactive measures you can take to prevent their unwelcome return.

First off, what are algae and where do they come from? Algae are living organisms that thrive in bodies of water, using photosynthesis and nutrients found in their surroundings to grow. Spores are everywhere and can be carried into your pool by the wind, rain, or even contaminated swimsuits and pool cleaning tools. Algae blooms can occur within a few hours when the conditions are right. Their growth can be accelerated by nitrates, phosphates, and carbon dioxide. Algae can develop in your pool due to a variety of factors, including insufficient water circulation, inadequate filtration, and unbalanced chemical levels.


What Problems Can Pool Algae Cause?

While algae are a natural part of aquatic ecosystems, their presence in swimming pools is undesirable and poses certain risks to both swimmer and equipment health.

  • Slippery surfaces - Algae can cause your pool surfaces to become slimy and slick. This sliminess poses a slip hazard for swimmers, increasing the risk of accidents and injuries.
  • Cloudy or discolored water - Algae growth in swimming pools can lead to aesthetic problems, causing the water to appear green, cloudy, or discolored.
  • Bacteria and contaminants - Algae-infested water can harbor bacteria and other microorganisms causing skin irritations, eye infections, and respiratory issues.
  • Maintenance expenses - Algae can hinder the effectiveness of pool sanitizers, making it more challenging to maintain clean and safe swimming conditions. Pool owners may need to invest in algaecides, shock treatments, and increased filtration to combat and prevent algae growth.
  • Equipment damage - Algae can clog filters, reduce water circulation, and foster the growth of other contaminants. This leads to increased maintenance, higher energy costs, and possible damage to pool equipment. Some types of algae, such as yellow and black algae, can cause a host of different problems such as scaling and equipment degradation as well.

Types of Algae

In order to prevent the unseemly risks from algae, you’ll want to understand where they can be growing and the different types you might encounter. Aside from your pump and filtration system, pool lights, ladder treads, and other small crevices are all targets for algae. Now, let’s dive into the different types of algae.

Green Algae - Green algae is the most common type of pool algae, usually caused by inadequate filtration or sanitation. It thrives on the presence of sunlight and nutrients. Green algae prefer to float in free-standing pool water but have been known to cling to pool walls and bottoms. Once the algae have taken over, the water becomes cloudy with a hint of green. This green color comes from chlorophyll.

Yellow Algae - Also known as mustard algae, this wall-clinger can be a formidable foe. The yellowish-brown spots tend to grab onto pool walls, steps, and corners. Since it is sheet-forming, it can be quite difficult to eradicate. Did we mention it’s also resistant to chlorine? These algae can sneak into the pool filter or even cling to your swimsuit, skimmer basket, etc. Removal is a must once you see any signs of yellow algae growth.

Black Algae - This pesky algae strain is one of the toughest pool algae to kill. You may notice black spots stuck to the pool surface; these can be extremely difficult to remove due to the protective layers over the black algae plant. To make it even harder, their roots need to be destroyed or another will grow in its place. Black algae usually are introduced into the pool water by contaminated pool cleaning equipment or from someone who just came back from the beach. Similar to yellow algae, black algae can grow in normal sanitizing levels and proper filtration, making it a tricky opponent.

Pink Algae - This algae is more of a bacteria but can be annoying as well! Pink algae, also known as pink slime, usually shows as streaks in corners and crevices. It’s very rare for it to bloom over an entire pool due to its slow-spreading nature. Popular areas this algae likes to hang out are in low flow and circulation areas. It will attach itself to smooth surfaces, which doesn't bode well when using your pool cleaner or pool brush. 

Once you’ve determined which type of algae you’re dealing with, it’s time to learn how to remove algae from your pool.


Removing Pool Algae

Effectively removing pool algae requires a methodical approach. Especially with some of the nastier outbreaks, you may need to repeat steps multiple times in order to fully eradicate the pesky plants.

  • Skim & Vacuum - Our Pool Pros recommend starting out by using a skimmer and your vacuum to remove any large debris floating around your pool. This helps to make it easier to see and reach the rest of your pool to continue the process and prevents those larger pieces from being broken down in the shocking process.
  • Brush & Scrub - Next, use a pool brush to vigorously scrub the walls, floor, and any other surfaces where algae are present. Make sure to give your stairs and ladders extra attention during this step! This helps to break up the algae and expose it to the treatment. If you have steps, make sure to pay those extra attention as algae love small crevices and corners.
    • Make sure to scrub extra well when fighting mustard algae, as this algae loves to cling to surfaces.
    • If you are trying to combat black algae, consider using a steel bristle brush. In order for the chemicals to work on this stubborn type of algae, you need to tear through the protective layer. *If you have a vinyl liner, do NOT use a steel bristle brush.
  • Lower Your pH - A little Pool Pro secret, lower the pH levels to mid-to-lower sixes. By doing this you’re actually making the water more acidic, which really helps the shock work at a significantly more efficient level.
  • Shock Treatment - Next, use the appropriate shock treatments to kill the newly brushed and exposed algae. We recommend using pool shock at approximately 1 lb. per 10,000 gallons of water (check the pool shock manufacturer’s instructions for the recommended dosage).
    • When fighting mustard and black algae, you may need to use higher dosages, up to double or triple the normal amount.
  • Filter & Vacuum - After the shock treatment, run your pool filter for the next 24 hours to give your filtration system a chance to remove the algae. Clean the filter to remove any algae that may still be residing there. Remember that if your pool equipment isn’t clean, then your water supply won’t be clean either. Then, use a pool vacuum to suck up the remaining algae. If the algae aren’t completely gone by this point, repeat the previous steps until they are.
    • If your algae bloom was severe, you may want to vacuum prior to running the filter.
  • Test & Balance - At  this point, the algae should be history. Make sure you test your water and balance out the water chemistry in order to prevent further outbreaks. Check out our blog on achieving proper water chemistry to learn more.
  • Run Your Filter -  The best way to prevent algae from coming back is to run your filter for 24 hours a day. This may cost a little bit initially, but it both helps keep your water clean and is a huge algae deterrent, as algae thrives in stagnant water. In the long run, it’s cheaper and less time-consuming than dealing with an algae bloom.

If at any point you need more power to help get rid of that nasty algae, you can add in one of our algaecide products, such as the Doheny’s Total Algaecide or the Doheny’s Super Algaecide Plus. Not only does Doheny’s Total Algaecide help remove even the most stubborn algae, it also helps prevent algae growth for the next 90 days! Speaking of algae prevention, let’s get into learning how to stop algae from making their return.


Maintaining a Clean and Algae-Free Pool

Regular pool maintenance routines are crucial to prevent algae growth and ensure a safe swimming experience. Remember, it’s much easier and cheaper to prevent algae than it is to treat it!

  • Maintain Proper Water Chemistry - Regularly test and balance the pool water's pH, alkalinity, and chlorine levels. This creates an environment less conducive to algae growth.
  • Consistent Circulation - Ensure your pool's circulation system is functioning optimally and running as much as possible. Algae thrive in stagnant water, so keeping your water moving helps prevent their growth.
  • Sunlight Control - Use pool covers or strategically placed shade structures when possible to limit sunlight exposure. This helps reduce the conditions that encourage algae growth.
  • Regular Cleaning - Establish a consistent maintenance routine that includes skimming the pool surface to remove debris, brushing the pool walls and floor to loosen any algae, and vacuuming to eliminate dirt and algae spores. Promptly removing debris helps to eliminate potential nutrients for algae. Regularly clean and backwash the pool filter to ensure optimal filtration.
  • Shock Treatments - Periodically perform shock treatments, even if the water appears clear. This helps prevent algae from taking hold and keeps the pool water sanitized.
  • Shower Before Swimming - Ensure that swimmers practice good hygiene by showering before entering the pool. This helps to avoid the introduction of contaminants such as algae spores.
  • Algaecide Treatments - Various types of algaecides, such as Doheny’s Algaecide and Doheny’s Algaecide 60, are great for prevention of future algae outbreaks. Just pour in the recommended dosage once a week and you’ll be algae-free!

Swimming pools experiencing repeated algae blooms can be tested for phosphates. Heavy rainstorms can blow contaminants into the water from fertilizers or soil. Double-check your sanitation and balance as well. If even after all of those removal and preventative steps the algae persists for several years, it may be time to drain the pool. The dead algae cells can help revive the algae growth year after year. To combat the algae roots, use a chlorine wash or acid wash.


Algae in the Winter

When temperatures reach below 40°F, algae growth is stopped, but it can still survive and become dormant over the winter. Pool algae will come back to life weeks before you decide to open your pool.


Winter Algae Prevention Methods

  • Pool pH - Even when your pool is officially ‘closed’ for business, it is still a good idea to check the pH levels and maintain the range between 7.2-7.6 pH. If you notice that the chlorine levels are towards the higher end of the scale, this means that the chemicals aren’t killing off potential unseen bacteria that may be living in your pool walls and floor.
  • Shock the Pool - If you notice fluctuating pH readings after checking the pool pH, use pool shock at approximately 1 lb. per 7000 gallons of water (check the pool shock manufacturer’s instructions for the recommended dosage). Once pool shock is applied to the water, run the pool filter for 24 hours a day and re-test the water.
  • Look For Algae - If you still notice potential algae blooms after 12-24 hours of running the filtration system, then add a second dose of shock and repeat this step until you notice the algae has turned either gray or white-ish in color. If you notice the significant color change, this means the algae blooms are dead. Remove the algae from your water supply using an automatic pool cleaner or a pool vacuum right away.
  • Backwash Pool Filters - Remove your pool filters and clean them thoroughly with a garden hose or backwash them. You want to be sure all potential live and dead algae are completely gone from the area.
  • Winter Algaecide - As the winter weather in your area continues, take time every few weeks to observe the condition of your water supply. If you notice fluctuating pH levels, add some winter algaecide to the mix. Read the instructions on the label so you know exactly how much is needed per gallon.
  • Phosphate Remover - Consider using a phosphate remover as an additional precaution against winter algae blooms. Changes in the pool’s phosphate levels could be a direct cause of your algae problem. Pour it into the pool and run the filtration system accordingly. After approximately 24 hours, clean your pool and filters to be sure the phosphate remover has been completely removed. If any residual phosphate remover remains in your supply, it could cause problems down the road. Test the water, and if your phosphate levels are at 0, repeat Step B and shock the water to be absolutely sure that the nasty bacteria is gone for good.

By understanding the different types of pool algae, employing effective removal strategies, and adopting preventive measures, you can ensure your swimming pool remains a safe swimming environment. Regular maintenance and attention to water quality will keep algae at bay, allowing you to enjoy many great pool seasons.