How to Get Rid of Algae in Pools—And Prevent It From Coming Back
Make sure your summer goes swimmingly with an algae-free pool
You were looking forward to a summer full of pool parties—but you noticed some algae growth. Besides being an eyesore, pool algae can put the brakes on any fun you may have planned because it lowers your water quality. Green algae in pools is a common offender, though algae can also be yellow or black. Learn how to get rid of algae in pools so you can get back to lounging on your float and practicing your backstroke.
What Is Algae and What Causes It in a Pool?
Algae is a plant without any roots, leaves, or stems. It’s hard to miss algae when it starts growing in your pool, because you’ll notice clumps floating in the water or stains on pool surfaces.
When algae grows in your pool, it can cause lots of problems like unbalanced water chemicals, clogged filters, and poor water circulation.
There are many reasons that algae grows in pools, including:
Low or unstable chlorine levels
Low or high pH levels
Contamination from swimsuits or toys from natural waters like oceans, rivers, and lakes
Insufficient pool filtration
Poor water circulation
Extreme weather like heavy rain or high heat
Why Should You Quickly Remove Algae From Your Pool?
If left to grow unchecked, algae can clog pool filters, make your pool chemicals less effective, and keep your pool filtration system and skimmers from working at their best. Your pool water will struggle to circulate, making your pool dirtier and allowing algae to keep flourishing. This cycle can result in visible algae, discolored water, and the growth of bacteria that can be harmful to swimmers.
Even the smallest amount of algae in a pool can cause algae-eating bacteria to move in, and these bacteria can irritate pool users. For these reasons, remove algae from your pool right away with the following tips.
How to Get Rid of the Algae in Your Pool
There are a few measures you can take when it comes to tackling pool algae. Follow these steps to learn how to get rid of algae in your pool and how to clear a green pool.
Clean Your Pool
Your pool chlorine and filter alone won’t be able to battle the algae. In fact, getting rid of that unsightly algae is going to take a little bit of work—so roll up your sleeves and recruit some help from around the house, if you can.
Note that the process of getting rid of the algae is going to vary depending on the type of algae you have. Even if you’re hoping to clear cloudy pool water fast, you’ll need to follow step-by-step directions to get the job done right.
No matter the algae type you’re battling, the first step is doing a manual cleaning.
Scrub Your Pool
Begin by scrubbing your pool surfaces, including your floors, walls, and steps. Make sure to get all of the hard-to-reach places like corners and crevices. You should use the pool brush that’s suited for your pool liner type. For vinyl or fiberglass liners, use nylon brushes. If you have a concrete or gunite pool, use stainless steel brushes.
Vacuum Your Pool
Once you’re done scrubbing, it’s time to do a manual pool vacuuming of all of the algae that’s settled on your pool floor. Instead of vacuuming the algae through your filter, it’s usually best to use a waste line. Keep an eye on your water levels as you vacuum. If it dips six inches below the tile, you should pause, refill the pool, and then continue working.
Clean Pool Accessories
Another part of the manual cleaning is taking care of your bathing suits, toys, and other pool accessories that were exposed to natural bodies of water. Wash all of the bathing suits in your washer using bleach, and wipe down all toys and accessories with a solution of one tablespoon of bleach to one gallon of water.
Test Your Water
The next step is testing and balancing your water levels. Do this by using a pool water test kit and making sure your water falls within recommended levels. Pay special attention to your pH and alkalinity, because high pH (anything around 7.8 to 8.2) and alkalinity will hinder pool shock from doing its job. So if needed, learn how to lower pool pH and how to raise pH in pools.
The ideal chemical levels for your pool are:
pH between 7.2 and 7.6
Free chlorine between 1 to 3 ppm
Calcium hardness between 200 and 275
The following steps for removing algae from pools vary according to the type of algae.
Getting Rid of Green Algae in Pools
If you’re wondering why your pool is green, know that green algae in pools is more common than mustard yellow or black. The green color can range from a teal-green to black-green. This type of algae tends to stick to the pool walls, or you might find clumps of it floating in the water. And while it’s the easiest type of algae to get rid of, it also spreads very fast, so it’s a good idea to tackle the cleaning project sooner rather than later.
Shock Your Pool
Once you’ve completed the steps described above, you need to double-shock your pool with two pounds of shock for every 10,000 gallons of water. This process increases the chlorine levels in your pool and helps to kill the algae. It’s best to shock your pool in the evening or night, because the sun burns away unstabilized chlorine. Keep yourself safe during this process by using safety glasses and gloves.
Run Your Filter and Test Again
Run your filter and pump until the water clears up, which usually takes around 24 hours. And once your water clears up, test and balance your water again.
Finally, you need to take care of your pool filter. The process varies depending on the type of pool filter you own. You have the choice of soaking your filter cartridges in diluted muriatic acid, or getting a new one if you want to be absolutely sure you won’t reinfect the pool. If you have a DE filter, do a backwash.
Removing Mustard Algae
Mustard algae is less common than the green variety, and tends to grow only in humid climates in the Southern parts of the United States. It can look like pollen or sand, and sticks to walls and pool items.
After completing the pool cleaning steps mentioned above, you can get rid of mustard algae by triple-shocking the pool with three pounds of shock for every 10,000 gallons of water. Run the pump and filter for 24 hours until the algae is gone, and then test and balance your water.
Clean your filter cartridge or install a brand new replacement, and your pool should be back to normal.
Getting Rid of Black Algae
Black algae is the toughest type to get rid of. It’s often found in concrete, plaster, or gunite pools and rarely in fiberglass or vinyl liner pools.
For black algae, you may need to put in more elbow grease during the first step, which is the manual cleaning. Consider using a putty knife or a pumice stone to scrub off the black algae. And for the most stubborn stains, use a chlorine tablet and scrub it directly onto the surface.
After testing and balancing your water, you need to quadruple-shock the pool. That means using four pounds of shock for every 10,000 gallons of water. Then, run the pump and filter for 24 hours.
Usually, you’ll need to brush the pool again, and then shock the pool one more time. Once the pool clears up, test and balance the water. And in the final step, you need to take care of the pool filter. Clean the cartridge or get a new one.
Tips to Prevent Pool Algae from Returning
Considering how time-consuming algae removal can be, you’re probably eager to keep your pool algae-free. Here are the most important pool maintenance tips to help keep the algae from returning:
Maintain a regular pool cleaning routine, including brushing and vacuuming.
Test and balance your water levels weekly.
Shock your pool weekly.
Use algaecide preventatively (wait until chlorine is less than 5 ppm).
Ensure your filtration system is running smoothly all season long.
Always clean toys and swimwear after swimming in natural bodies of water.
Run your pump and filter eight to 12 hours a day all season long.
Rinse off before jumping in the pool.
Hire a local pool services company to perform regular maintenance and repairs.
DIY Algae Treatment vs. Hiring a Pro
You can DIY algae treatment for the cost of pool shock, which is $10 to $30 depending on how much you need. This is assuming that you have all of the other pool cleaning chemicals and tools you need on hand.
While it's a money-saver to do the job yourself, the process requires a lot of manual labor with all the scrubbing and vacuuming. Moreover, you have to deal with all the water testing and balancing, which can be a big job. And when you factor in all the time you need to do the pool shock and filter cleaning, you'll see that the process requires a significant time investment.
When you hire a pool services company, they’ll handle everything from start to end. It’s likely that the company will come to your house several times to do the chemical treatments, disassemble and clean your filters, and apply algaecide. You can expect this service to range between $250 to $500 or more.
Some companies will even drain, power wash, and sanitize your pool to ensure your algae won’t come back. This service starts at $300. In case you have leftover stains after the drain and clean, then you may need an acid wash, which starts at $600.
Mizuki Hisaka contributed to this piece.
Frequently Asked Questions
The best way to dissolve algae is using pool shock. The shock increases the free chlorine levels in your pool, which in turn kills bacteria, microorganisms, and algae. You can opt for granulated shock that you mix with water, or pre-mixed liquid shock.
Keep in mind that using pool shock is just one of the steps you need to take to get rid of algae from your pool. Unless you also brush, vacuum, and clean the filter, your algae problem may return.
Yes, when you add shock to your pool, it raises the free chlorine levels in the water, which in turn kills bacteria and algae. It’s worth noting that although you may think of using algaecide to get rid of algae, it’s actually a preventative measure.
Additionally, killing the algae alone isn’t sufficient to get your pool back to normal. You need to vacuum, brush, clean the filter, and balance the water.
You shouldn’t swim in a pool with algae. When there’s algae, there’s also bacteria that’s feeding on the algae. Also, algae-infested pool water is often chemically imbalanced, which means germs like Cryptosporidium, Giardia, and E.coli could be present. These germs can cause a range of illnesses from gastrointestinal issues, to rashes, and respiratory problems.
The best thing to do is to get rid of the algae first, test and balance the water, and then you can enjoy swimming without any worries.
Depending on the severity of your algae problem, it can take 24 hours to five days to clear up your pool completely. It depends on how long it takes to test and balance your water, as well as if you need to repeat any of the algae-cleaning steps.
Even though it might be a drag to have your pool out of commission for so long, it’s best to be patient and get the job done right.
Figuring out how to clear a green pool can seem tricky at first, but it’s all about knowing which pool cleaning chemicals to use. You may think of using baking soda to help you with your algae problem, but unfortunately, it won’t help. This is because baking soda only raises your pH and alkalinity levels.
Instead, you need to use pool shock to clear up a green pool—the shock raises the free chlorine levels and will kill the algae.
Yes, you should vacuum algae out of the pool, but only after brushing the walls and floors. You can vacuum algae through a waste line or through the filter, but the former is a better option whenever possible.
Once you finish the vacuuming job, you can move on to testing and balancing the water, and then using pool shock to kill the algae.