How to eliminate and prevent green algae in a swimming pool

How to Eliminate and Prevent Green Algae in a Swimming Pool / One of the biggest challenges of maintaining a swimming pool is to prevent algae growth. Even if the pool has an excellent filtration system and proper sanitation, eliminating green algae from the pool is a hard task.

What is Algae? Algae is an aquatic organism that grows on pools that are not properly maintained. The commonly found algae are green in color, though algae in black, pink and yellow are also found. It grows in both sun and shade and needs light to grow. Algae in a swimming pool affect its overall appearance, that swimmers hesitate to use it. Though algae are not dangerous as such, pools with algae can be a breeding ground for other types of pathogens like E-coli bacteria.

What Causes Algae in Pools?

Any of the below factors can cause algae in a pool.

  • Poor water circulation

The water in a swimming pool should never be stagnant. If it does not circulate properly, or if the circulation is poor, it can result in the formation of algae.

  • Poor water balance

The swimming pool water should have an ideal level of pH balance, calcium, alkalinity and cyanuric acid. If this balance is not maintained, it can result in the growth of algae.

  • Poor sanitation

Adding chlorine to water not only eliminates dirt but also helps to kill bacteria and algae. If the pool does not have the correct level of chlorine, it can result in the formation of algae.

  • Poor filtration

Filtration helps remove dirt and other debris in the water, which plays a crucial role in the formation of algae. Thus, if the water is not filtered or the filtration process is poor, it can result in algae growth.

How To Eliminate Algae In Swimming Pool?

As soon as you notice algae growth in your swimming pool, you should try to get rid of it. You can follow the below steps to eliminate algae.

  • Check the water qualit.

First, you should check the water to see whether it has the right amount of chlorine, pH and stabilizer. If the balance is not maintained correctly, you should add the required chemicals to maintain the water quality. The pH level of water should always be maintained between 7.2 and 7.6.

  • Clean the filter

The main function of the filter is to clear all the debris and sediments. If you have algae in the pool, the filter is more likely to have those sediments. You should clean the filter depending on what type it is.

  • Brush the pool

With the help of a pool cleaning brush, you should thoroughly brush and clean the floor of the pool, the walls, and the step. Brushing and cleaning help to remove any algae that got stuck on the surface.

  • Shock the pool

Shocking is the process of adding chemicals like chlorine at a high dose in the water. This helps to destroy algae and other bacteria in the pool. It is best to shock the pool during the evening or night as the sun’s rays can burn the chlorine off before killing the algae.

  • Test the pool water

Once the shocking is done, you should check whether the water has proper chlorine and pH level. If chlorine level is very low, you should undertake the shocking process after a few days.

  • Add algaecide

Algaecide is a chemical that helps to kill algae present in water. A day after the shocking is done, you should add algaecide to the pool and leave it for 24 hours. Adding algaecide helps to kill all the algae in the pool.

  • Brush and vacuum the pool

Now brush the pool once more to remove all traces of algae. Remember to brush all parts of the pool, including the steps. Use a pool vacuum cleaner to suck out algae and other debris.

  • Run the filter

Once the whole process is over, you should continuously run the filter for a day to clear the water.

How To Prevent Green Algae in Swimming Pool?

  • Good circulation system

The pool should have a good circulation system to prevent the growth of algae. You should regularly check the skimmer and pump strainer basket and clean it. This helps the water and sanitising chemicals flow throughout the pool.

Along with this, you should also clean the pool filter at regular intervals. Over time, the filter gets clogged with debris and sand. Cleaning them regularly ensures that the pool remains clean.

  • Maintain the sanitizer level

Green algae grow continuously in the pool. But they can be kept under control through the use of sanitizer or chlorine. Thus, you should check the sanitiser at regular intervals to ensure that they are maintained at the prescribed level.

Using a floating or an automatic chlorinator is the best way to maintain the chlorine level in the pool.

  • Shock the pool regularly

The pool should be shocked at least once a week to prevent the growth of algae. Shocking helps to keep the pool clean and kills the algae before it grows.

  • Clean the pool regularly

Cleaning the pool through regular brushing helps to prevent the growth of algae. You should pay special attention to all parts of the pool, including the floor, wall and steps. Brushing prevents the algae from burrowing the root inside small cracks, which later becomes very difficult to remove.

Once the pool is brushed, you should vacuum it thoroughly. While brushing, algae and other debris separate from the surface and settle at the bottom of the pool. This should be vacuumed and cleaned thoroughly to prevent further growth of algae.


Algae can grow anytime and destroy the very appearance of the pool. Thus, you must keep a watchful eye on the pool year round. You should maintain a weekly cleaning schedule and try to stick to it. Special attention should be paid to the ladder and step as algae growth in these areas can go unnoticed. Maintaining a neat and clean pool is the solution to all your algae problems.

There are a variety of algae species occurring in different habitats in the world such as fresh water, marine, desert sand and snow. These photosynthetic organisms are vital since aquatic animals feed on the organic matter they produce. Algae also take up excess nutrients such as phosphate, ammonia and nitrate, which can intoxicate marine life from the water. Algae grow fast in warm temperatures and water and when there is a lot of organic material in the water. However, algae blooms may result in mortality of aquatic life, since they affect the PH of the water.

Optimal Conditions for Algae Growth

Most algae thrive and multiply in water with high pH levels ranging between seven and nine. The optimum pH for most algae species is 8.2 to 8.7. Neutral or lower water pH decreases the growth of algae. Algae, like other plants, utilize light to photosynthesize food for growth. Low temperatures slow algae growth, which blooms and multiplies in warm temperatures of approximately 16 to 27 degrees.

  • Most algae thrive and multiply in water with high pH levels ranging between seven and nine.
  • Low temperatures slow algae growth, which blooms and multiplies in warm temperatures of approximately 16 to 27 degrees.

PH Effects During the Day

Disadvantages of the Greenhouse Effect

During the day, photosynthesis takes place, due to the presence of sunlight. Algae draw carbon dioxide from the water to utilize during photosynthesis, promoting cell growth. Removal of carbon dioxide from the water raises the pH levels, as a result of the reduction in carbonate and bicarbonate levels of water, since they are used to replenish the lost carbon dioxide. Depletion of inorganic carbon from water by algae results in high pH levels, as evidenced by the rise in pH levels of natural waters, which can go up to 10 or beyond in the presence of algae. The rise of water pH also causes ionization of ammonia which is detrimental to aquatic life.

  • During the day, photosynthesis takes place, due to the presence of sunlight.
  • Removal of carbon dioxide from the water raises the pH levels, as a result of the reduction in carbonate and bicarbonate levels of water, since they are used to replenish the lost carbon dioxide.

PH Effects at Night

At night, no photosynthesis takes place, so algae stops taking in carbon dioxide from water and goes into a respiratory stage 1. During this respiratory stage, algae consume oxygen that was produced during photosynthesis and release carbon dioxide into the water 1. This increased production of carbon dioxide decreases the pH levels in the water at night. Therefore, it is essential to control the algae growth, since they compete for oxygen with other aquatic animals at night.

Implications of Algae Effectson pH

The Advantages of Rainfall

As stated above, algae cause pH fluctuations in water during the day and at night 1. These pH fluctuations cause stress in aquatic animals and might lead to death or interfere with growth. Large numbers of algae are likely to cause more pH fluctuations, thus it is important to control algae blooms. Algae growth can be minimized by planting water plants such as water lilies, which will be competing for nutrients and light with the algae.

Swimming pool problems in Florida are never fun to deal with, especially Green Algae blooms. Green algae often appears as a greenish color on the walls and/or bottom of the pool or a greenish coloring of your swimming pool water. The easiest way to avoid green algae blooms is by using a professional swimming pool maintenance company, like Crown Pools! If your’re managing your swimming pool care, continue reading and we’ll discuss some of the information you should know to avoid swimming pool downtime caused by green algae.

How to eliminate and prevent green algae in a swimming pool

To kill green algae, you need to use Chlorine-based swimming pool “shock”. Shock is a granular form of highly concentrated chlorine, which quickly raises the chlorine level of the swimming pool water, killing off all of the algae. Pro Tip: Ask us about Pool Ionization systems which can keep algae away permanently.

Expedite The Removal of your Algae Bloom

  1. Brush the walls and floor of your swimming pool, loosening the algae and exposing more of it to the Shock
  2. Ensure that your pH level is between 7.2 – 7.6
  3. If your swimming pool does not show considerable improvement after 24 hours, consider another “shock” treatment
  4. Dead algae appears white or a grayish color. When you cannot see any green or greenish tint in your swimming pool, vacuum thoroughly.
  5. Clean or “back wash” your filter, to ensure that you don’t leave any dead algae trapped inside the filter. If you skip this step, your risk of another algae bloom increases!
  6. Test and balance all of your swimming pool chemicals. If you would rather be 100% sure, call your local swimming pool professional and we’ll come out to help ensure your pool is balanced.
  7. Ask a swimming pool professional about Algaecides and Phosphates, which can help prevent future algae blooms.

From full-service swimming pool cleaning and maintenance to individual service calls, the technicians at Crown Pools provide the highest level of professionalism and quality swimming pool care in Florida. Whether we handle your entire swimming pool maintenance program or only cleaning/chemicals, we offer free delivery — always on time and at competitive prices. If you’re looking for a swimming pool company in Jacksonville, look no further than Crown Pools, Inc. – See more at: Swimming Pool Maintenance

A swimming pool that has greenish water contains microscopic green algae. This is a common occurrence after spring or summer, when algae spores flock into the water, carried by air or rain. Many people think that unpleasant visual is the only thing green algae causes in the swimming pool, but there are various health and security risks associated with them.

When you get out of the greenish water and experience slimy sensation on your skin, it may be caused by algae that stick to your body (and swimsuit). Slimy algae layer around the pool is dangerous because it causes a slip hazard. People may hit their head on something hard, break a bone, or drown because of the slippery surface caused by algae.

Green algae also cause a headache for swimming pool guards, because the greenish tinge makes it difficult for them to spot a drowning person. Unlike what movies may tell you, a drowning person often struggles silently, without causing big splashes or commotion, and pool guards need sharp eyes to spot such person. Green algae in the water do not help.

Finally, there are health risks from bacteria that thrive in the algae colony. Illnesses such as diarrhea and Escherichia coli contamination may be caused by bacteria that live in the oxygen-rich environment among green algae. The Centers for Disease Control and Prevention even has a specific page to discuss fecal bacteria that thrive in the algae-rich pool.

Killing Green Algae with Chlorine (Shocking)

How to eliminate and prevent green algae in a swimming pool

Killing Green Algae with Chlorine /

Light algae problem may only need skimming, a little sanitation, filter-cleaning, and pH-balancing to remove. However, when basic “official” methods no longer work due to stubborn algae, you can try “shocking”. This refers to a method of killing algae by exposing them to a large amount of chlorine. Here are three ways to do it:

1. Light chlorination

Light chlorination is for a pool that only has little algae, with slightly faded green color. The recommended dosage is 500 grams of chlorine for 40,000 liters of pool water.

2. Medium chlorination

Medium chlorination is used to a pool that already has darker green color, although you may still be able to see the bottom. You need around 1,500 grams of chlorine for 40,000 liters of water.

3. Extreme chlorination

Extreme chlorination is for pool with a very thick layer of green algae, resulting in dark and muddy green color. You need at least 2,000 grams of chlorine per 40,000 liters of water to remove such algae.

You must use special liquid chlorine made for cleaning a swimming pool. Make sure to do the shocking method at night, before sunlight will reduce chlorine’s performance to remove algae. Also, avoid pouring chlorine right into the skimmer.

Killing Algae Using Algaecide

How to eliminate and prevent green algae in a swimming pool

Killing Algae Using Algaecide /

Algaecide is a straightforward method to kill green algae, but it is a heavily toxic substance. Make sure you have no other options before trying this method and follow all the instructions in the package carefully. If you are unsure, call professional pool cleaner to treat your swimming pool with algaecide.

If your pool has turned dark green, regular algaecide will not work. You must use the product with at least extra 30 percent of active ingredients. You can also buy copper-based products, which can kill green algae more quickly than regular products. However, copper-based products can stain your pool after a while.

If the algae problem is light, and you do not have enough money for copper-based products, the cheap quaternary ammonia-based algaecide is enough. However, it can cause annoying foam on the surface of the water.

Finally, if you want to pour another substance, wait at least 24 hours after applying the algaecide.

Removing Algae with Floc Method

How to eliminate and prevent green algae in a swimming pool

Remove algae with floc /

Floc method is perfect if you refuse algaecide or chlorine-related solutions. This method uses a chemical that can bind floating particles, submerging them to the bottom. Once they go down, you can vacuum and clean the pool. The steps are longer than the previous two, but the result is quite effective.

Pouring the floc requires you to turn on the recycle function in the pool’s valve. This is to help the floc chemicals circulated properly, without going through the filter. Floc is available in powder and liquid. Make sure you choose the right one, based on your budgets and pool condition. Read the labels to use it properly. Once the chemicals are poured based on directions, you can leave it overnight.

When all the particles finally come down, switch the valve to waste, and vacuum the waste particles. Add clean water to the pool by pouring it from the garden hose when you vacuum the particles. Depending on the volume of your pool, you may need to stop several times until the flying particles settle again.

What to Do after Cleaning

You can try various methods to remove green algae from the pool, even if the algae have thrived. However, the best method is to keep green algae from accumulating.

Achieve this by regulating water pH (between 7.4 and 7.6), maintaining the filter, cleaning the pool regularly, and closing it when necessary to prevent chemicals that can encourage algae growth, such as fertilizer.

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Picture this: summer has begun and your family wants to kick things off with a good old fashioned cook out. You buy the burgers, tidy the yard, and uncover the pool – only to find that your water is a green, swampy mess. Yep – you’ve got algae, my friend.

What can you do to eliminate algae? Ask the experts.

If you ask the pool experts at PoolXperts, they’ll tell you the answer is simple: shock the water, use an algaecide, and vacuum up what’s left behind. This method will work, but it’s not the only way.

Here are a few solutions that will help you eliminate any algae you may find in your pool with products you may have at home.

Black Algae

Black algae is one of the most aggravating strains around – and that’s saying something since all algae is pretty aggravating. You often find this menacing algae growing roots on your pool walls, leaving black dots that are sure to ruin your pool day.

If you encounter black algae, you’d better roll up your sleeves because you have some scrubbing to do. Grab a brush and some baking soda. Bicarbonate, the active ingredient in baking soda, is an effective spot treatment to help kill the algae and loosen it from the wall. Make sure you really get every last particle free; black algae has particularly long and stubborn roots which makes it a persistent strand. With enough scrubbing you can banish the black algae for good.

How to eliminate and prevent green algae in a swimming pool

Ariel by Solar-Breeze

Mustard Algae

If you notice a brown or yellow algae settling on your pool walls or floor, it’s once again time to reach for the scrub brush. R egular cleansers often have a hard time reaching mustard algae because it tends to collect at low water levels. Fortunately, this strain of algae is far less stubborn than black algae. Good scrubbing, vacuuming, and water balancing should clear it up.

It is important to note that re-infection is very common with mustard algae. This algae can survive on pool toys like floaties or noodles, and it can even escape treatment by hiding in the pool filter. It can also live within your trusty scrub brush, undoing all your hard work! Inspect and clean all your pool supplies and accessories when you notice mustard algae.

Blue/Green Algae

Blue or green algae is the most common strain of pool algae, but it is no less difficult to clean. Green algae clings to the walls of your pool, but can also be free floating which creates murky, swamp-like film over the water. You guessed it – you’ll need the good ole’ scrub brush and some borax.

In the same way that baking soda can be a spot treatment for black algae, household borax does the same for blue and green algae. Simply use the borax to scrub away algae that’s sticking to your pool walls, then use the brush to dislodge it. Follow up by vacuuming up or scooping out the free-floating algae. You will have a much easier time once the borax has stopped the algae from blooming.

Eliminate Algae of All Types

The goal is to never have algae. Test your water regularly, keep your filter clean and in good working order, and be sure to treat your water after big pool parties. Using a floating pool skimmer and chemical dispenser like the Solar-Breeze NX2 or newest Ariel by Solar-Breeze will remove debris from the surface of your pool before it has a chance to sink, decay, and turn into food for algae. With careful pool maintenance, algae can be one thing you do not have to worry about.

How to eliminate and prevent green algae in a swimming pool

You don't need harsh chemicals to treat the algae in your pool.

Help! My Pool Is Green!

It's a hot summer day and the sun is bright—perfect weather for taking a dip in your pool. You venture out to the backyard to check out the pool you haven't used since last summer. Lo and behold, it's green!

You take a closer look and see green, yellow, even black algae growing in your pool. You know it can't be safe to swim in that infested water—plus it's just gross and slimy. How on earth did this happen?

What Causes Algae in a Swimming Pool?

Algae are plant organisms that grow where it is warm, wet, and sunny. Of course that's a perfect description of most swimming pools in the summertime, yes?

Algae spores can drift into the pool on the wind, or people can bring spores into the pool via dirt and leaves they've come into contact with. Certain nutrients often found in pools, like phosphate, can actually help the algae grow. Phospate can enter the pool through people, dirt, leaves, and even some chemicals.

Some organisms that we call algae, such as blue-green algae, black algae, and pink algae, are actually bacteria. Either way, algae is also a breeding ground for bacteria, which means it is potentially not safe to come into contact with it.

During those hot summer months when the sun is beating down on your swimming pool, algae is given the perfect environment in which to grow. This is especially true when the pool has not been cleaned or treated.

Pool Algae Removal: Cotton Ball Method

Vacuum the Pool (for Above-Ground Pools)

If you have an above-ground pool, you probably use a vacuum to clean out all of the debris.

The problem, however, is that most of the vacuums that are made for these kinds of pools use mesh bags to pick up the debris. Much of the debris—including the algae—will slip right through the mesh and go back into the pool you are vacuuming.

So what can you do to get rid of the algae?

How to Modify the Mesh Bag to Pick Up the Algae

I've discovered two different workaround fixes for this problem. Both fixes involve modifying the mesh bag so that it collects the small debris that usually escapes it. These solutions work well with the Intex above-ground pools, for example.

Proper maintenance is essential to keeping your pool spotless, but the presence of algae can be a stubborn, uninvited guest that’s hard to get rid of.

With the tips in this article, you’ll be able to fully remove dead algae in your pool, and keep it away for good.

How Dead Algae Gets Into Your Pool

One day, you may notice the floor of your pool covered in dead algae, and chances are you’re not even sure that’s what it is.

Algae comes in a few different variations: yellow, green, black, and pink. If your pool experiences an algae bloom, the chlorine in water kicks in and tries to kill as much of it as it can. As it breaks down the algae, the offending particles are sent through the skimmer, and the filter removes them from the pool water.

So then, why is there a bunch of dead algae still on the floor?

This is because algae particles are so fine, some of them settle to the bottom of the pool, instead of being sent to the filter. When dead algae settles, it will look like a grey or brown dust has infested the floor.

Note: Dirt can sometimes be mistaken for dead algae at the bottom of the pool. If you can easily capture it between your fingers, it’s probably dirt. No stress, we have a separate guide on how to get rid of dirt.

Is Dead Algae A Problem?

Aside from looking aesthetically unpleasing, leaving dead algae in the pool means there’s particles still floating around in the water, which your filter will try to clean up.

This can lessen the lifespan of the filter (depending on how much algae is present. Additionally, dead algae can stain your pool surface if left on it too long.

How To Remove Dead Algae From Your Pool

There are solutions to eradicate algae from your pool.

You should be aware that if the algae is still green, it’s not dead yet. Additionally, some pool owners use these methods and discover more dead algae the day after cleaning.

If any of those are your case, the pool still has algae in it and it will just keep coming back. You’ll need to shock the pool (or SLAM it), to make sure every single microorganism is obliterated.

Brush Your Pool

Brushing down the pool walls is going to be the first step you need to take, loosening and removing algae that’s clinging to them.

Depending on your pool’s finish you may need a soft bristle brush (for fiberglass or vinyl liner pools), or a steel bristle brush (for concrete and plaster finishes).

By brushing the walls, it allows the algae to float in the water where it can be pumped out and filtered, or fall to the floor of the pool.

Use A Pool Vacuum

The most effective tool to get rid of dead algae is a pool vacuum, and there are two ways you can remove algae using a vacuum.

The first method is the better (and easier) of the two, and can only be done if you have a multiport system, using either a suction-side or pressure-side vacuum. The multiport system allows you to send the waste water completely out of the pool.

To begin, set the system to its “waste” setting. Depending on the vacuum, it connects to either the skimmer (suction-side) or a dedicated suction line (pressure-side).

With this “vacuuming to waste” method, the algae is vacuumed up, goes through the pipes and pump, and is then sent out of the pool system, bypassing the filter. This not only protects the filter from clogging, but also ensures algae won’t be reintroduced to the pool.

Also, it’s important to keep your skimmer basket and pump basket in place during this process, as they’ll help catch large clumps. If they’re removed, these clumps can clog up your pipes, and potentially damage your system.

The second method (if you don’t have a multiport system), is sending it straight through to your filter.

An older filter would be preferable as this process will render it useless when it’s over. Vacuuming algae through the filter can be less effective and a big headache as you’ll need to clean out the filter multiple times during the process.

As for vacuums themselves, the robotic kind are the best ones for this job as you just turn them on and let them do their thing.

However, manually vacuuming out your pool can get the job done just as well. It’s also important to make sure the vacuum won’t damage delicate pool surfaces like vinyl liners.

Use Flocculant

Adding pool flocculant to your water will coagulate the algae, clumping it up, and causing it to sink to the bottom of the pool. Flocculant works similar to pool clarifier, but clarifier clumps remain on the surface of the water to be skimmed off.

Sinking the clumps makes it easy for the vacuum to suck them up. However, only use pool floc if you’re vacuuming to waste, as these clumps will clog the filter and could cause potential damage.

How To Prevent Dead Algae In Your Pool

Preventing dead algae in your pool means preventing it from forming in the first place. It’s the best plan of action and means you may never have to deal with this pool pest if you stay on top of things.

Balance Your Chemistry

Regularly balancing the water chemistry (particularly the chlorine), is important because algae thrives in high pH environments that have low sanitization levels.

The ideal pH level for your pool is between 7.4 and 7.6. The total alkalinity of the water should measure between 80 and 120 ppm. Maintaining both of these will keep the water in a neutral state, which are ideal conditions for keeping algae away.

When it comes to your sanitizing chemicals, chlorine should always be kept between 1 and 3 ppm, and shocking the pool on a regular basis is also important.

Most pool owners will shock at least once per week. This process entails adding a mass dose of chlorine to kill off every single contaminant in the pool. When it comes to algae, shocking is a proactive measure to keep it away.

Phosphate levels in the water from swimmers and other organic matter can contribute to algae blooms, but if you’re on top water testing, and using an algaecide (see below) you can greatly reduce the chances of algae ever being an issue.

Keep Your Filter Clean

Maintaining the filter by cleaning it regularly is important not just for algae prevention, but for general pool maintenance as well.

The filter is usually working an average of 8 hours every day, so make sure you’re cleaning it out before it becomes ineffective and problematic.

Depending on your filter type, you can backwash a sand or DE filter, whereas a cartridge filter will have to be manually cleaned.

Use Algaecide Proactively

Algaecide is a pool chemical that will kill and prevent algae from growing in the pool, and is so effective as a preventative measure that some pool owners regularly add it to their water after its weekly shock treatment.

Dosing the pool with the right amount is critical, as too much can cause eye and skin irritation, as well as foaming that can damage your pool’s filter.

It’s Dead And Gone!

The good news here is that dead algae in the pool is a curable problem.

With the right know-how and proper prevention techniques, you can return your pool to a pristine state with very little work required.

What's that green, yellow, or black slime in your pool?

How to eliminate and prevent green algae in a swimming pool

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If you can think back to your science class you may recall that algae are one-celled plants. And if you happen to be one of those algae, you are not alone: there are more than 20,000 varieties.

In a swimming pool or spa, algae are those green, brown, yellow, black, or pinkish slime that resemble fur growing on the steps and in corners — places where circulation may not be optimum. The majority of swimming pools are exposed to several hours of sunlight per day, and it’s sunlight that will speed up algae growth.

If you notice an increase in algae growth, run the pump more often. Also keep the water balanced, which means more frequent testing. It may seem obvious, but remove things from the pool, such as floats, inflatable toys, leaves, and grass. Make a real effort to keep it clean. The following algae colors are described and remedies are recommended in The Ultimate Guide to Pool Maintenance by Terry Tamminen.

Here's how to identify and get rid of certain types of pool algae.

Green Algae

Green algae — chlorophyta — is a slimy substance that can be found on pool and spa surfaces. First signs of it appear in small clusters on pool steps or lurking in corners. It's at this stage that you should start to attack it — green algae can grow quickly in 24 hours or less.

Brushing will remove green algae, but it won't destroy it. Superchlorination, aka shocking or shock treatment, will sanitize pool water that might be resistant to normal chlorination. Maintaining your pool regularly during swim season is key to staying on top of a green algae outbreak.

Yellow Algae

Yellow algae also goes by the appetizing term "mustard algae," because of its brownish or muddy yellow color. While yellow algae (phaeophyta) doesn't spread as quickly as green algae, it is harder to destroy.

Like green algae, yellow algae grows in the same fur or mold-like pattern. Unlike green algae, brushing will not do much to remove it, although it will remove the top layer of slime, which exposes the algae underneath. Superchlorination and regular maintenance will help kill mustard algae.

Black or Blue-Green Algae

Black and blue-green algae are one and the same. Primarily found in lakes and ponds, it does find a home in unmaintained pools. According to author Tamminen, black algae is "the pool technician's worst nightmare." He continues, "at the first sign of black algae, you need to consider the pool or spa as a patient in critical condition."  

Why? Unlike green or yellow, black algae doesn't have that outer layer of slime, which acts as a protective barrier for the algae underneath. Black algae will penetrate deeply into hard surfaces, like plaster and concrete. It first appears as black spots and then proliferates. If you see signs of it, immediately use a stainless steel brush, which cracks the algae's shell and allows sanitizers to penetrate it.

Blue-green algae were formerly known as cyanobacteria, a blue photosynthetic bacteria that live in water or damp soil.

Pink Algae

A bacteria, pink algae appear as a reddish-orangeish slime, usually at a swimming pool's water line. It is also attracted to PVC surfaces in a pool, especially piping. It seems to keep company with white water mold, which is a fungus. Of all its colorful cousins, pink algae are the easiest to maintain. Simple brushing and regular sanitizing should keep it under control. If it has gotten out of hand, remove it, then shock it with a calcium hypochlorite shock.

Blog for swimming pool owners, Care & Repair, Buyer's Guides and Pool Fun information

How to eliminate and prevent green algae in a swimming poolIf your pool opens up green every spring, this post is for you. Here’s some ways to prevent a green pool opening, and be confident of a blue pool when the cover comes off.

Pools open green when the winter cover is not keeping out debris, the water chemistry is poor, and there is inadequate sanitizer.

Even if you open late, and even if you have a mesh safety cover – you can skip the stains and discoloration by avoiding these problems with the pool cover and the winter water chemistry.

Winter Pool Cover ProblemsHow to eliminate and prevent green algae in a swimming pool

If you want to open to a blue pool every year, I have a simple solution. Install a solid safety cover, without drain panels.

I’ve opened 1000’s of pools in my time, and those with a solid-solid safety cover would always open up blue, and usually crystal clear. Keeping out winter air pollution, pollen and dust, by blocking all rainfall and snowmelt keeps the water in balance and conserves winter chemicals.

Raised Walls: For pools with a raised wall, for a raised spa or higher deck level, there are two ways to install a safety cover – in-the-wall or up-and-over. In-the-wall installations may not fit so well, and fill with leaves during winter. It’s always best to go up-and-over on pools with raised walls.

Floating solid pool covers, with water bags, can be a very good cover, if they are conscientiously pumped off, and kept clean. They are prone to easy holes however, from sticks or animals, and when they get a hole in the middle of winter – if you aren’t maintaining it very well, a sinkhole can develop and spill dark green matter into your pool.

The problem with floating solid covers, is that they never fail to fail, right in the middle of winter, or when you’re struggling to remove that last bit of mucky water from the surface – rip! there goes a seam, or a small hole opens up to a gash.

Winter Water Chemistry Problems

If you close your pool clean, with water balanced, and a winter kit, or an appropriate amount of sanitizer and algaecide, you can expect those chemicals to last about 5 months.

For pools that open green each year, something extra is needed. I use Pool Magic with Phos Free for problem pools. Pools that have green spring openings usually have a phosphate problem, although they may also have cover problems and/or water level problems.

The most important thing to note with winter pool chemicals is that more will be needed if you have contaminants entering the pool, be they full sized leaves, or dust that washes off the trees. More will also be needed when the temperature of the water rises.

Water Temperature Problems

When your water temperature drops into the 50’s and colder, most danger of algae is suspended. Chemicals also last longer when the water is cold. But when the water temps warm up in the spring, your chemical protection can be quickly depleted. Above 65 degrees, and winter chemicals in an unfiltered pool will become active and begin to work themselves to death.

Winter chemicals are really most needed just after closing and just before opening. During the colder months, very little is going on under the cover, but as things heat up, more chemicals are consumed, and more organisms spring to life. Mesh covers will allow some sunlight to pass through which can warm the pool surface.

Mesh Covered Pool Problems

How to eliminate and prevent green algae in a swimming poolMesh safety covers and solid covers with drain panels, let in all sorts of microscopic gunk during the winter. If the pool water level is allowed to touch the underside of the cover, leaves get stuck on the cover, and a tea bag effect is created, leaching the tannins from the leaves to create a leaf soup, staining pools and consuming chemicals.

Water balance can change dramatically in a mesh covered pool. It should be checked at some point during the spring. It’s a good idea to add an extra dose of shock or algaecide (but not both) as the weather begins to warm up into the 60’s.

My advice is the same to all mesh covered pool owners.

‘In mid to late spring, or about a month before you plan to open the pool:’

  1. Remove springs on both sides of the pool. Fold cover onto itself in the center.
  2. Use a small submersible pump or a siphon to lower water below the tile.
  3. Check and balance the water chemistry and shock the pool, or add a Qt. of algaecide.
  4. Find the chlorine floater and fill it with tablets.
  5. Brush the walls on both sides of the pool.
  6. Put the pool cover back on tightly.

If you open up to a green pool each spring, think if you have any of these problems above, Fixing one or more of them can give you a beautiful blue pool next spring!