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How to Deal with a Green Salt Water Pool

W hen you went to sleep, your pool was looking normal, maybe a bit cloudy, but you admitted that it has been extensively used lately and it may be time for a cleanup the following days. But this morning, it seems like a vengeful witch came over the night, stole your beautiful blue salt water pool, and replaced it with a marsh. You are wondering how is this possible without you noticing any sign. And how much will it get you to bring it to its previous state?

The good news is that you can solve this difficulty in less than a day. So, if you have friends coming over for a weekend pool party, you will probably not have the postpone. But the measures need to be drastic and aggressive. It’s time to get armed with your old scrubbing brushes and get ready to pour some strong chemicals into the water. If you follow the steps below, you will wake up the next day and see that a fairy brought you back your blue waters.

Discover the best salt water pool systems in our top and analyze each product’s specifications and features. Compare prices and see our recommendations. Get your own unit and start enjoying automatic chlorination that will bring you more free time to spend in the pool.

A pool filled with algae and water Image

Why Did My Pool Turn Green?

A saltwater unit is supposed to extract the Cl in the NaCl and blend it with the water, thus ensuring chlorination, which should kill microorganisms. So, why isn’t this working, and what is that green thing in the pool?

This is a situation that occurs both in salt water and chlorine models. Even if you are trying to preserve the environment balanced, a single moment of negligence can ruin everything. The pH can drop under the optimal values, increasing the acidity, or the free chlorine can become insufficient for the number of contaminants. This is why super chlorination is practiced in both types of units.

However, even if most salt water kits come with this option, sometimes the quantity of chlorine they release may still not be enough. Plus, the pressure on the generator can be pretty big. It is why we recommend the old pool shocking method.

But first, let’s take a look at the contaminants that can make the water turn green:

Green Algae

They are showing up in most of the units, and it is the chlorophyll that lends them the color. They utilize the process of photosynthesis to feed themselves, so they thrive in an environment with lots of sunlight, just like your pool. The bad news here is that they multiply extremely fast (this is why you found your pool filled with them overnight), so you need to act fast. As soon as you have spotted something green on the walls or floor get scrubbing and prepare for chemical treatment.

Mustard Algae

They are harder to treat as they have become chlorine-resistant. You will spot them on the pool’s surfaces, looking like soft sand or pollen. Nevertheless, don’t let yourself fooled as they can spread and cloud the water. Check closely and make sure to buy a larger quantity of sanitizer.

Black Algae

This is the nightmare of every pool owner. They spread fast and stick their spores deep into the surfaces. They are hard to remove and kill. But not impossible. Although they rarely appear in salt waters, they can find their way there and will appear in the form of dark spots in the corners and even along the grout lines.

Pink Slime

This is not algae but something more dangerous, namely a bacteria. If you see it appearing on the soft surfaces of the pool, get ready to remove it fast, as you wouldn’t want to expose your family to it.

Algae won’t deposit on the walls if they get scrubbed periodically. Check out our excellent selection of pressure-side pool cleaners and pick an energy-efficient unit with independent navigation and strong brushes that can make maintenance a breeze.

A pool filled with algae and debris Image

Is It Safe to Swim in a Green Salt Water Pool?

Algae on their own are not harmful, but as they develop, multiply, and die, they can cause other phenomena to happen. First of all, they are a good environment for bacteria to flourish, so water that is filled with algae can expose you to infections. Secondly, if they cover the waterline, they can make swimming more difficult and even pose a danger for kids who will find it more difficult to get out of the water. And last but not least. If they die and settle at the bottom, they can make it slippery and raise the risk of accidents.

But besides all these, most people find swimming in a unit with algae disgusting. You wouldn’t go swimming in a marsh, so make sure your friends and family won’t need to find excuses not to use it.

If you keep the pool covered, contaminants won’t be able to settle in. Find out how a solar pool cover works here and decide if you need one. The best about these products is that you will only need to press a button and the unit will be covered or uncovered. Plus, the energy is all free.


How to Treat It – Super Chlorination Step by Step

Having identified the causes, it’s time to combine the power of your muscles with the eradicating force of chlorine and unleash them against the marsh monster. Step by step, you will eradicate all the contaminants in the pool.

Here’s how:

Step 1 – Give Your Pool a Good Scrub

Use a brush to remove the contaminants from the surfaces. Make sure to cover the whole surface, even if it seems clean. Moss fragments or spores are the ones getting started the colonies but can be really tiny at first. This will be the toughest job you have to perform so don’t be afraid to put all your energy into it. The more moss you clean from the walls, the more successful the operation will be, as the residue will then interact with chlorine and get deactivated.

Step 2 – Vacuum the Pool

Your water is now even cloudier and dirtier than at the beginning, but this is how the process goes. It will look a lot worse before it looks better. Now it is time to get your pool vacuum cleaner and get down to debris removal. Be persistent. Clean all the contaminants, even if you may have to add more water afterward.

Step 3 – Test the Water

It is important to determine if the algae invasion was caused by a low pH, unbalanced alkalinity, or not enough chlorine. Use a digital pool test to determine the values. The pH value should be between 7.4 and 7.6, while the alkalinity level should remain between 120 and 150 ppm. If one of these variables is out of balance, make sure to bring them to the optimal values. This won’t kill moss but will help you maintain the pool clean afterward.

After dealing with these aspects, measure free and total chlorine levels, and calculate combined chlorine by extracting free Cl from total Cl.

A glass filled with sample green water Image

Step 4 – Shock the Water

Read the instructions on the chlorine shock package and combine the right quantity with water. This will help you establish the dose that needs to be used depending on the size of the unit. Nevertheless, you may need to add more doses, depending on the type of algae populating the environment:

  • Small Invasion of Green Algae – 2 x Shock Dose
  • Large Invasion of Green Algae – 3 x Shock Dose
  • Black Algae – 4 x Shock Dose
  • Pink Bacteria – 4 x Shock Dose

Prepare the solution into a 5-gallon bucket. Arm yourself with gloves and wear some old clothes, then pour the solution into the water, while walking slowly around the pool. Make note that the pump should run while you perform this operation. Let it run for at least 8 hours afterward until the filter clears all the residue and the water becomes clear.

Apply shock treatment after sunset to obtain the best results. The sun can act upon the chlorine and evaporate it, making the treatment inefficient.

Step 5 – Is the Water Still Green or Cloudy?

If the problem hasn’t been solved, shock again. On the other hand, if the water is only cloudy, you can utilize a pool clarifier, which will help gather together small specks and form clogs, which will be easier to catch by the filter. If the issue persists, you may be dealing with other problems. Check the pH again. If it is too acidic, it may favor the presence of copper, which can alter the color.

Step 6 – Clean or Replace the Filter

Open your sand or D.E. filter and thoroughly clean it. If you haven’t performed this operation in a while, now may be a good moment to replace it with a new one. Note that this step is essential, otherwise, all of your work could have been in vain. The large residue could clog it and make the filtration inefficient, and this is exactly what can make your water turn milky again.

Check out our best above-ground pool kits. All the models are designed for quick installation and are compatible with a saltwater generator. Get a new pool for your family the easy way.

Pool clean vacuum Image

How to Prevent This Phenomenon from Happening Again

As you have seen, you will be putting a lot of work into removing algae, so wouldn’t it be better to take some precautions and stop the green pool phenomenon from happening? We have some good advice that can help you keep the marsh monster away:

  • Test the water weekly – Even if it is your system’s job to do it, it never hurts to be extra careful. If the chemicals are off, use the super chlorination function or shock the pool yourself to make sure an optimal level of chlorine is preserved.
  • Shower before swimming – You can cause water contamination with dust, cosmetic oils and creams, and even spores, so a quick shower is appropriate to preserve the cleanness of the pool for longer.
  • Wash your swimming gear – Especially if you use it in public pools as well. Make sure your swimsuit doesn’t carry the algae from one pool to another.
  • Ensure excellent hygiene – Clean the surfaces once a week and use a pool cleaner vacuum to remove gunk from the water. This action can be performed by a robotic pool cleaner if you don’t have the time or are not willing to put up with the effort.
  • Algae are brought by the wind along with dust and pollen, which are some of the most common contaminants. You can reduce their action by installing a pool cover and keeping the water protected when it isn’t utilized.

The Bottom Line

Green pools are a nice prop addition only in horror movies. Unless you are preparing for Halloween, you should take care of yours and not let it become a health hazard for your kids. Even if you have installed a salt water generator, it is a good idea to make some pool shock supplies and apply this treatment weekly, especially if you had algae problems in the past. And always test the water. It is the chemical unbalance the one that allows algae to grow and bacteria to own the water.

Lexie Thorne
Lexie Thorne
Lexie is the newest member of the team, previously working for a local business that sold, among other items, robotic vacuums. She takes a keen interest in the latest tech and considers herself to be a veritable tech geek. Using her connections, Lexie makes sure that she always talks to experts when putting together reviews and articles to ensure the information you read is reliable and makes a difference toward aiding you to better understand how automated devices for home use work.
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