How to Fix a Green Salt Water Swimming Pool

Eliminate the algae today and enjoy your clean clear swimming pool

It is not pretty when algae are floating around in your saltwater pool. Nothing is attractive about the swampy backyard appearance that algae create. If you want to change this appearance, you must act immediately by killing the existing algae and preventing more algae from returning. This action is not as difficult as it may seem, but it requires you to act fast and aggressively.

It doesn’t take much time for algae to grow. If you procrastinate on this problem, then you’ll have a severe algae crisis in your pool water. Then it becomes extremely difficult to remove the algae. But if you follow a few basic steps right away, you can remove the algae before it spreads and gets out of hand. You just need some elbow grease, a few pieces of equipment, and certain chemicals.

Why Does Algae Form in Salt Water Pools?

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Your pool water can go from clear to milky in a matter of days. If you notice strange colors in your water like black, yellow, or green, then you know you have a problem. How do you suppose this nasty stuff got in your pool in the first place?

You might assume that airborne algae just fly into your pool water from the open wind. The truth is that most algae are brought into the water by the people who go in it. Algae spores attach themselves to people’s bathing suits, swim vests, cleaning equipment, and floats. Once these objects enter the water, the algae spores find a new home where they can thrive. The result is slimy colorful patches which float on top of the water.

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Types of Pool Algae 

You can’t treat algae effectively unless you learn about the various types of algae, as well as the algae imposters. You must treat algae aggressively, or else it’ll rebound quickly into a swampy mess in your pool.

Green Algae

Green algae are cyanobacteria known as Chlorophyta. It contains a green chemical called chlorophyll, which is where the name comes from. Every green plant gets its color from this chemical. Green algae multiply and spread quickly in pool water. You can hinder their growth by adding more chlorine to the water. Cloudy water that turns green is a clear sign of green algae growth.

Yellow Algae

Yellow algae are known as mustard algae. Check your pool floor or corners to see if there is any yellowish debris there. It may look like clumps of sand or pollen. If you see this debris, then you have yellow algae.

Black Algae

Even though this is a form of cyanobacteria, it is not real algae. The interior of your pool may have black spots form across its rough surfaces. These black spots are not as harmless as they might seem. They’ll get absorbed into the deepest areas of your pool walls and make your pool chlorine resistant.

Pink Slime

When pink slime is visible near the components of your pool, it is bacteria rather than algae. Obviously, it is not a great idea to swim in water that is filled with bacteria, so be sure to treat your water immediately after you see this pink slime form.

Chlorinating Salt Water

Saltwater pools are chlorinated, just like regular pools. You actually use the same amount of chlorine in both types of pools. The only difference is in the way you administer the sanitizing chemicals to the water.

Rather than adding chlorine to your pool water, you add salt instead. You use something called a salt-chlorine generator to convert the salt into the chlorine compound known as sodium hypochlorite, and hypochlorous acid.

When saltwater enters the chlorinator, there is an electrolysis process that zaps the salt and makes it become chlorine. Only small amounts of chlorine are generated at a time. This allows the chlorine to circulate throughout the pool water slowly. That way, swimmers won’t incur as much irritation to their eyes, skin, and hair.

Unfortunately, the slow distribution of chlorine in the saltwater system will increase the likelihood of algae growth and unbalanced water chemistry.

Super Chlorination

If you want your saltwater chlorinator to have 100% chlorine output for one full day, you can probably make that happen. That means your pool water will have a much higher concentration of free chlorine in it. This type of “super chlorination” is only a good idea after several swimmers have used your pool. It is also good to use when a lot of rainwater has been added to your pool or if your water simply looks cloudy. It is good to do a super chlorination act at least one time per week. This will ensure the contaminants stay away from the water. The only thing a chlorine boost like this won’t do is prevent algae.

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The Algae Removal Process

You can’t depend on a chlorinator to get rid of algae from your saltwater pool. So, you need to use chemicals and basic pool equipment instead.

Elbow Grease

An algae brush can be used to scrub the walls and floor of your pool. Your goal is to free as many algae from your pool walls as possible. If there is any residue leftover, you can use chlorine to treat it. Just make sure you’ve scrubbed away the upper layers first.


You’ll have loose algae debris floating in the water. Use a manual vacuum to remove this debris by sucking it up. Set the vacuum to waste so that the algae don’t make its way back into the water. Once you’re done, the water levels may have decreased because you sucked some water up too. Now you’ll need to add more water to the pool until it is back to its normal water level.

Pool Maintenance

Keep testing the water of your pool to ensure its water chemistry is balanced. Do this after each time you vacuum the water too. If the levels of alkalinity and pH are off, then add more chemicals to balance these levels out. After you do that, you can add a lot of chlorine to the water.

Super Shock Treatment

The following shock dosing chart can help you figure out how much shock treatment to add to your pool water.

A small amount of green algae: Two times the regular shock treatment.

A large amount of dark green algae: Three times the regular shock treatment.

Mustard algae (any amount): Since mustard algae are more resistant to chlorine, you need a triple shock treatment in this case.

Black algae: Four times the normal shock treatment.

Pink Slime: This is not algae. It is bacteria. Only a quadruple shock can take care of bacteria issues.

Algae Panning

After you shock your pool water with a lot of chlorine, it’ll still look cloudy because of all the dead algae spores floating around. This is normal, though. Just turn on your filtration system and leave it on overnight for 8 hours or more. By that time, there shouldn’t be any more cloudiness in your pool water. But if you still see cloudiness, add some pool water clarifier and repeat the same filtration process again.

Test the Water Again

Your water should look clear at this point. Now you must normalize the level of sanitizer in your water. Test your water with test strips to see what the level is at. Tweak the sanitizer levels if necessary.


Your filtration system works hard to remove algae spores from the water. However, you must be careful that old algae spores don’t get back into the water via the return lies. Remove the filter and use muriatic acid to give the filter a deep cleaning. This will stop the spores from returning.

Alternatively, a filter replacement might be warranted too. Anyone who uses a sand filter or diatomaceous earth filter should backwash to waste first. This will tell you whether the filter needs to get replaced.

Prevention Methods

Aside from algaecide being used to care for your salt pool water, here are some more ways to prevent algae growth in saltwater pools.

Take a shower prior to entering your pool. This washes away algae spores which may be on your swimwear. Not only that, but the shower may wash away contaminants that you put on your body like shampoos, lotions, and conditioners. If you were to enter the pool with these contaminants on you, then the sanitizer would be focused on killing them instead of the algae.

When you’re done using the swimsuits, wash them again. You never know what might have gotten onto your swimsuit when it was in the water. This might not be a problem if you used your home pool, but it may be a problem if you used a public pool.

After using pool equipment and toys, be sure to clean them. Use diluted bleach to wipe down your pool accessories and equipment in order to eliminate mildew and algae spores. Rinse everything to avoid the bleach degrading your accessories.

Test and balance the chemistry of your water each week.

Utilize the boost mode of your chlorinator to maintain your chlorine pool levels each week. If a lot of people have used your poll, then use the boost mode every evening rather than every week.


Remember that saltwater pools are not algae resistant. You must do your part in killing and preventing algae using the methods described in this article. Then you can safely enjoy a good swim in your pool water with your family and friends.

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