You have the most rigorous cleaning schedule and closed your pool correctly last winter, but it still happens - you open up your pool or are ready to swim, and your water isn’t as crystal clear as you’re used to. So what causes water to go green, and more importantly, what can you do to eliminate it?
There’s only really one answer - Algae.
So, what is Algae?
Algae are simple, mostly aquatic organisms that produce their own food by converting sunlight into energy.
There are three types that may be in your pool, and there are different ways to deal with each one.
Green Algae
Green algae are the most common algae, and (luckily!) are the easiest to kill. Green algae in your pool can be a light teal green to a dark, blackish green throughout your pool.
Yellow Algae
Also known as Mustard Algae, yellow algae is a rarer form of algae mostly found in humid climates. Rather than covering the entirety of your pool like green algae, yellow algae look more like globs of pollen or sand that cling to dark, shady corners of your pool.
Black Algae
Black algae are not algae at all but bacteria. Their roots can dig into your pool's concrete surfaces, making them extremely difficult to kill. They are tough to get rid of and grow back quickly if you aren’t thorough enough to completely get rid of them.
If you get to it early enough, you can remove the early stages of algae growth with a pool flocculant.
If your filter has a multiport valve, shut off your pump and turn the valve to recirculate or recycle. This will mix the flocculant around without filtering it out of the water before it’s done its job.
Add the recommended dosage of flocculant to your pool - if you’re using our recommended Rx Clear® Super Floc Clarifier, that’s 2 lbs. per 10,000 gallons of water.
Circulate your water for 2 hours, then shut off your pump and let it sit for 24-48 hours. The flocculant will bind to the algae and settle on the pool floor, ready to be vacuumed.
Turn the multiport valve set to waste so dirty water doesn’t blast back into your pool through your return lines when you begin to vacuum.
Hook up your backwash hose to the backwash/waste port. Direct your wastewater appropriately.
Vacuum your pool. Work slowly to remove all the thick sediment from the bottom. If the water becomes too cloudy, you may need to stop and allow the particles to settle again before continuing to vacuum.
Add water while you’re vacuuming to maintain your pool’s water level
Double shock immediately after vacuuming to remove any remaining algae. You may also want to brush the pool sides and floor before shocking
Run your filter until the water clears
Killing algae with Chlorine needn’t be a chore, but just make sure to be thorough as you brush and vacuum your pool. If you leave any algal spores, the algae will be back before too long.
Automatic pool cleaners can be a lifesaver when it comes to pool maintenance, but they may not be the best choice when it comes to cleaning algae. They aren’t designed to deal with algae. Therefore, it’s better to vacuum your pool using your filter’s waste setting manually (this prevents contaminated and algae-filled water from recirculating back into your pool).
As you vacuum, pay special attention to areas where algae bloom. It’s also important to top up your pool as you vacuum so the water level remains halfway up your skimmer.
It’s time to use some elbow grease. Scrub the algae off your pool walls to help the chlorine penetrate any remaining algae. This also loosens up the contaminants so they can be killed and filtered out efficiently.
Using a stiff pool brush on a telescopic pole, brush the floor and walls of your pool, paying special attention to the corners, crevices, and any shady areas where algae is often the worst. It’s normal for your water to get cloudier the more you brush, so it’s easiest to brush the tougher spots before moving on to lighter spots. Then, when the algae is loosened off the surfaces, use a tile and vinyl cleaner to ensure all the spores are gone.
Use Test Strips (we recommend Rx Clear) or a Liquid Test Kit to test your alkalinity and pH. Why test the water before you shock it? Because correcting the pH and alkalinity will ensure that your shock is the most effective against algae.
Shocking your swimming pool is the process of super chlorinating your water to kill the algae in it. The more algae you have in your water, the more shock you’ll need to kill it and get your water sparkling again.
We recommend Rx Clear® Multi-Functional 4-in-1 Shock for killing algae and other bacteria in your pool. Follow the package instructions to determine the dose for your pool size (our recommended dose is 1 lb per 10,000 gallons) and multiply it depending on the kind of algae you have.
Once the bag is opened, make sure you use all its contents! If any granules settle at the bottom of the pool, use your pool brush to disperse them. After this is done, put your cleaning equipment (like the pool brush and vacuum head) in the shallow end of your pool so the shock will sanitize the tools at the same time.
Shock needs to be used at dusk or night because the sun can destroy chlorine before it can kill the algae.
Run your filter for eight hours or overnight to circulate the shock. If there’s still a significant amount of algae left in your pool come morning, repeat the brushing and shocking process again. Don’t panic if the pool is cloudy or slightly blue—we will deal with that in the next step!
After the shock treatment kills the algae in your pool, the water will turn cloudy blue.
When the algae in your pool dies, it turns from green to grey, and this dead algae needs to be filtered out. Run your filter continuously for at least 8 hours or until the water fully clears up. You can use Water Clarifier to speed up this process (we recommend Rx Clear® Super Clarifier).
It’s vital to ensure that your water chemical levels are balanced and the chlorine levels are back to normal before anyone gets back into the water. Adjust your alkalinity, pH, and chlorine levels as needed. Since you've removed water from your pool and replaced it with fresh water, you may also want to test all other water levels, such as your cyanuric acid and calcium hardness.
A lot of contaminated water just went through your filter to be processed, and the last thing that you want is a dirty filter that adds algal spores back into your pool, now you’ve worked so hard to clear it.
Deep clean your filter cartridges by soaking them in diluted muriatic acid or replacing them entirely. If you have a sand or D.E. filter, backwash it.
If you have dark green or black algae, or if your algae is more stubborn, you may need to repeat this process one or two times. Although this may be frustrating, it’s worse to do all of this hard work just for leftover algae to grow back into a big problem!
Algaecide is excellent for killing a small amount of algae, but it’s not recommended for use to get rid of a significant algae problem. There's also the risk that it can introduce a lot of copper to your pool.
Algaecide is suitable for early-stage algae growth, small amounts of algae, or as a preventative measure. Algaecide is also helpful in killing off lingering algae after you’ve cleaned your pool. It will help kill remaining algae particles before they’re filtered out.
Pools turn green when they’re full of Algae. These are simple, mostly aquatic organisms that use sunlight to produce their own food. Luckily, it’s straightforward to eliminate it by following the above steps.
It’s generally advised not to swim in a green pool. Algae can harbor bacteria that can harm people swimming in it, cause skin irritation and infections, and make surfaces slippery, increasing the chance of slipping or falling around or in the pool.
Algae can even occur in saltwater pools, but don’t worry. The steps are exactly the same as fixing a chlorinated pool. Simply follow the process detailed above to get your water back to normal.
Unfortunately, a green pool can’t be fixed overnight. The steps above may take several days to complete, so you should start well before you want to swim in your pool.
Shocking is definitely a step in clearing a green pool! However, you should brush the walls and floor of your pool to ensure you can get rid of all the spores and balance your water to make shocking your pool the most effective.
