How To Remove Algae Stains From Pool Walls

It is pleasing and completely relaxing to lower your body into a swimming pool, but at the same time, you are required to give your best to make the water swimmable. A swimming pool’s water condition depends on many factors that can independently distort your pool’s condition from beautiful to stinking if left unattended.

How To Remove Algae Stains From Pool Walls

Alga growths are among the common issues swimming pool owners encounter. Alga is tiny plants, but they lack the proper body structure of plants.

They exist commonly in black, pink, green, and yellow colors, whose presence mainly announces their existence. Alga is natural, and they grow in any type of water left untreated or with favorable water conditions.

They don’t grow in a day, so if it has reached the stage of staining your pool’s walls, you should first know you have been lagging in cleaning your swimming pool.


Can You Remove Algae Stains From Pool Walls?

It is easy to clean off algae stains with the proper methodologies and equipment without exposing yourself to harsh chemicals or dangers. Put to mind that algae stain removal isn’t the same as algae removal.

When you actively eliminate algae in your swimming pool, there will still be stains on the tiles created by strong algae that have been attached for a long time. There are usually misconceptions about differentiating if the stains are metallic or just the algae-caused ones.

Algae stains are usually green or brown. If the stains exist in other colors, it is most likely to be a metallic stain that will require another cleansing approach.

Before you remove the algae stains, you have to remove the algae present in the swimming pool.


How To Remove Algae In A Swimming Pool

1. Chlorine addition:

The algae in the swimming pool is caused by a low level of chlorine. In a pool with an adequate amount of chlorine, the alga isn’t common to be present.

Ultraviolet ray intervention, rainfall, heavy storm, debris, leaves, twigs, and other factors reduce chlorine levels. Now that the algae are obvious, an ordinary chlorine addition wouldn’t be practical.

Instead, shocking will be advised. Shocking is an advanced addition of chlorine aimed to make the chlorine level reach a very high stage and eliminate fungi, algae, chloramines, pathogens, and any other germs in the swimming pool.


You can get a pool shock from your local store and apply it according to the manufacturer’s instructions. Remember that pool shock comes in Sodium Dichloro-S-Triazinetrione, Calcium hypochlorite, or Potassium monopersulfate. Potassium monopersulfate is preferable if your pool is a vinyl type.

Calcium hypochlorite works best for commercial pools. Anyone you are recommended or choose to use; the next thing is to know the size of your swimming pool.

For a pool with 10,000 gallons of water, you should add a liquid pool shock of 1 pound, but since we target the elimination of algae, the amount of shock should be doubled. This means 2 lbs for 10,000 gallons of water.


The following steps are the application steps:

  • Test for the water’s pH and balance it with pH enhancers or suppressors to reach a range of 7.1 – 7.3. This will make the pool shock work effectively.
  • Run the filter system to remove dirt, debris, and any loose particles it can capture.
  • Turn off the filter and follow the personal preventive measures recommended by your pool shock product in the user’s manual.
  • Target applying the pool shock in the evening or when there is no sunlight.
  • Calculate the required amount for your pool and pour the pool shock through the edges.
  • Run the filter system for the circulation of the shock.
  • Turn off the filter after some minutes.

After the application, there will be noticeable differences in the spread of the algae. Turn on the filter to clear off dead algae. If algae persist after this application, you can reapply the pool shock after 24 hours.


2. Increased speed of circulation:

Area of stagnant water accommodates algae. If the water jets are faulty or clogged and don’t reach some areas in the swimming pool, it can lead to algae growth. Check for clogged water jets.

If you don’t notice any misappropriation, run the water pump with increased speed and time duration. Before this, you can position the water jets to be inclined a bit. This will make the water flow from their spine and create more force in water circulation.


3. Flocculation or coagulation:

You can purchase an algae flocculator or coagulator in your local pool store or through online pool platforms. Add the coagulant to the swimming pool, and the algae will form into groups. After that, turn on the filter system, and the coagulated algae will be easy to be drawn out of the water. You can merge this with other methods of algae removal, like shocking.


4. Algaecide:

There are different types of algaecide you can purchase and apply to your pool. Since it is a chemical, you are advised to protect yourself from the odor and direct body contact with the toxic chemical constituents.

Wear protective clothing, eye protection, and gloves. In windy weather conditions, be more cautious. Algaecides are effective for algae removal, but they usually come with incredible distortion in other water conditions.

The levels of chlorine, Total dissolved solids (TDS), bromine, calcium, pH, cyanuric acid, muriatic acid, acidity, and other components will be disturbed with the introduction of the algaecide. You will need to rebalance the proportion after the algaecide application.


Copper-based algaecides are the most effective, but the costs are pretty expensive, and they also stain the pool wall. Quaternary ammonia algaecides foam in water, but they are cheap and effective. Most algaecides aren’t fully capable of killing algae in a case where the bloom is high. They only do their parts, and you will still have a lot of algae living in the swimming. Request for an algaecide with over 30% active ingredients if you are in this condition. Nonetheless, you are advised to check if other means of removing algae are accessible before considering algaecides.


Note: Don’t combine algaecide with any other chemical. They will both explode or cause chemical pollution to the swimming pool water.


5. Raising the acidity of the swimming pool water:

This method isn’t among the commonly used steps to eliminate algae, but some home swimming pool users utilize it. Under a high acid level, algae wouldn’t be able to live.

They will die inside and come off through the filter as dirt. For this, you must lower the level of pH to around 3 or 4. After one or two days, the algae present would be weak enough, and you will add coagulants to collate them in sections.


You can lower the pH through the application of:

  • Industrial acidity improvers: Visit any nearby pool store and ask for acidity improvers or pH inhibitors. Explain to the sales representative or pool counselor present that you want to increase the level of your pool’s pH because of the presence of algae. You will be given recommendations on using the products and precautions to follow.
  • Vinegar: You can easily get this at home or your local store. For a swimming pool of 500 gallons, you should add ¼ cup of vinegar. For the application, sprinkle the right amount of vinegar for the surface area of your pool through the surface of the swimming pool evenly. You can stir the water using a plastic pipe or anything that wouldn’t contaminate the water for circulation. After 24 hours, you can recheck the algae level present, and you will be convinced the vinegar application worked.
  • Muriatic acid: It is a form of hydrochloric acid. It eliminates germs, kills microbes, destroys algae, and limits the growth of pathogens in the water. It is colorless, but it has a pungent odor. You can purchase it in your local store but don’t forget to ask for advice on the application methodology according to the product bought. Since it is toxic, you must wear safety clothing and avoid breathing the smell.

There are other series of methods to lower the pH of your swimming pool. After the application on the first day, you can add it again two days after. You can then filter the water and balance the pH back with any of:

  • Industrial alkalinity enhancers
  • Sodium bicarbonate (Baking soda)
  • Sodium hypochlorite (Bleach)
  • Borax

Read: How To Remove Green Algae Stains From Pool Walls

Removing The Algae Stains

After successful trials of eliminating the growth of algae in the swimming pool, you can then attempt to clean off the leftover stains on the pool walls. It is much easier to carry out stain removal unless in some rare cases. But with the weakening of the algae, you should encounter no difficulty.

1. Use of swimming pool brushes:

Scrub the floor and wall of the swimming pool with a pool brush rigorously. Make sure you put on protective footwear.

Pay more attention to areas with more coagulated portions of algae or stains. Components like the pool’s ladder, skimmer bottom, and the steps are more likely to host a hidden collection of algae.

If you don’t scrub them at once, there can be algae outbreak from the sections. You are advised to use a metal brush for concrete swimming pools and nylon brushes for vinyl pools.


2. Vacuuming:

You can use a specialized swimming pool vacuum to scrub off the algae stains or dead cells present in the pool. Continue this until the pool’s walls are sparkling clean.

This shouldn’t give you any problem since the earlier proceedings advised would have done 70% of the algae removal, and all you will be left with will be little.

If there is difficulty getting every dead alga, you can add coagulants to lessen the work done. This will make the algae sum up in visible sections, and you will be able to go straight to any collection.

This will make the process faster and easier. If your filtration system is of good output capability, it should be able to clear off the cells after chemical addition. This means you wouldn’t need to use the vacuum then.


3. Muriatic acid addition

The stains would get removed even after rigorous brushing and vacuuming for some areas. All you have to do is add muriatic acid directly to the spot and scrub. It should become transparent, but if not entirely, you can try the next day again.


4. Clean the water filters

When the water filters are clogged with particles, there will be difficulty in the optimized circulation of water, allowing the presence of algae. Check the filters and clean off the dirt. If you skip this part, there are high possibilities you will have to take the whole stain removal processes weeks after weeks as algae will grow fast in the water.

Removing algae stains isn’t usually a day’s work. You have to destroy the algae present, clear off the dead cells and scrub the remaining stains. All these might take days depending on the stains’ spread, but usually, it is just a week’s work.

Read How To Remove Black Algae Stains From Pool Walls?


What Causes Alga Presence In Swimming Pool Water?

  • Poor sanitation and water condition: if the chemical constituents present in the swimming pool aren’t of normal portions, algae grow exponentially in them, especially if the alkalinity is high. pH should be in the range of 7.2 and 7.6. Calcium level should be 220pm, and cyanuric acid level should be between 30 to 50. A reduced chlorine level also contributes to the existence of algae in the pool.
  • Irregular filtration and circulation processes: If the filtrations system is faulty, there wouldn’t be required water circulation, which will leave the algae to grow without hindrances.
  • Dirt and environmental exposures: If there are trees around or your pool is open to many twigs, leaves, and other organic materials, algae presence will be doubled. There will be nutrients to feed on, and the materials might introduce algae themselves. You need a skimmer to collect these materials over time and filter them off.


Read: How To Remove Yellow Algae Stains From Pool Walls



Can The Stain Be Removed Permanently?

Absolutely. You can remove the stains caused by algae, but only if your approach is sound. For black algae stains, you wouldn’t be able to remove them through ordinary brushing.

You will be required to add muriatic acid to the brush to scrub it off. Plus, it will require you to make the process more than once—maybe three more times before it clears off. If you shock the pool, maybe after two consecutive shocks.

Do I have to drain it before I remove the algae stains?

It is not necessary. In fact, for most of the methods recommended for algae removals, you will need the water to be of a certain level in the swimming pool.

Preventive measures against algae growth and staining

  1. Regular filtration
  2. Optimized water circulation
  3. Regular balancing of water chemical constituents.
  4. The occasional addition of algaecides attacks any micro growth of algae that isn’t visible.


Final Thoughts

You can brush off the stains without adding anything, and the walls will be transparent, but if you don’t destroy the algae present first, it will cause further problems soon.

Who wouldn’t even want to destroy visible algae and go on to cleaning the pool walls? Almost nobody.

You must follow the safety rules and precautions stated with each method recommended. All that is left is for you to take action.

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