Best Ways to Prevent and Avoid the Dreaded Black Algae in Your Pool

It is important to know how to avoid and prevent the dreaded black algae from ruining your pool. You can do so by following our guide of common questions and answers to better know what it is and how to protect it.

No one likes to see black algae in their pool, but it’s not something that you can just get rid of with a couple of quick fixes.

Fortunately, if you’re willing to put in the effort and time, it’s possible to remove it from your pool and keep future infections from occurring. But be warned- black algae is aggressive and stubborn when fighting for survival.

Black Algae

Black algae can potentially be very harmful to your pool’s natural balance, even if it doesn’t seem like a big deal at first. It will also clog up your filters and make it harder to clean the entire pool properly.

In this article, you’ll have a better understanding of what black algae is, why it’s terrible for your pool, and how to avoid it manifesting in your pool in the future.

How Do You Know if Your Pool Is Infested With Black Algae?

See if the algae in your pool have changed colors. If it was previously green and has now turned black, then chances are you have black algae in your pool. Check for floating bits of debris that feel slimy or soft to the touch, too- these can be an indication of this type of algae as well as giving off a musty smell.

To see if your pool is infested with black algae, observe more of these symptoms:

  • Black specks or strings on the pool floor that look like dirt but are actually algae spots.
  • If you see tiny plants in the water instead of a clear surface, then it’s likely that your pool is invested with black algae.
  • A blue/green tint to the liquids (pool water). Sulfur compounds cause this from the black algae reacting to sunlight.
  • You may also notice yellowish or brownish streaks running down the block walls of an enclosed pool; this is also caused by high levels of arsenic in both stagnant and moving pools. 

If you notice any of these manifestations, then you should get rid of black algae as soon as possible. 

How to Eliminate Black Algae From Your Pool

Black algae is a type of nuisance algae that thrives in warm, low-light pools. Black algae are not some sort of plant, but instead, it’s bacteria, which makes it harder to kill than green algae.

If allowed to continue to grow, it can cover the entire surface area of a pool and produce other types of algae and bacteria.

To remove black algae from your pool, here’s what we advised you to do, so you’ll be back in your pool in no time. Removal can be challenging but not impossible with the right tools. So, before you start, here are some materials that you might need. 

  • Pool brush and pole
  • Pool shock treatment
  • Algaecide
  • Chlorine tablets
  • Granular chlorine
  • Nylon brush

Sanitize the Tools You’ll Be Using

One of the essential steps in fighting black algae is to make sure that you sanitize your tools before and after using them. For example, pool brushes, poles, hands, and any other items that come into contact with the water should be sanitized before you start removing black algae from your pool.

Sanitizing these items will help prevent new infections of black algae from forming over and over.

Clean Your Pool’s Filters

It’s essential to ensure that your pool’s filters are cleaned regularly. The reason for this is that black algae will grow quickly in a warm, low-light pool and release more toxins into the water than other types of algae and bacteria.

The presence of these toxic substances in the water will cause all sorts of problems for your health- not just infection and health issues, but also damage to your pool equipment and system performance.

Scrub the Walls and Bottom of Your Pool as Many Times as It Takes

Black Algae: Scrub the Walls and Bottom of Your Pool as Many Times as It Takes

Left to its own devices, black algae will form and spread rampantly in a pool very quickly. Unfortunately, they’re often harder to remove than other types of algae as well.

To start with, scrub your pool walls and bottom with a pool brush and pole. Then, get right into the corners of the surface area if you can so that black algae don’t get a chance to grow elsewhere.

After that, scrub again with your brush using chlorine tablets or liquid to prevent any new infections from forming over time, as well as kill off and get rid of the current growths while they’re still small enough.

Clean Your Pool Deck and Pool Furniture

Black Algae: Pool Deck

It’s important to make sure that your pool deck and the furniture around it are cleaned of any algae growth as well. To kill black algae, you’ll need to spray it with chlorine or algaecide. Make sure not to use bleach- this will only make things worse!

The pool walls hold a lot of black algae spots and can lead to health issues for humans. By scrubbing the walls as many times as it takes, you can remove these black algae and prevent potential health issues.

It’s Time for Pool Shocking

Black Algae: Pool Shocking

Shock your pool at least twice when trying to remove black algae. This will help to kill off the algae on a surface area where it’s present and prevent other types of algae from growing over time.

The key is to make sure that the time between shock treatments is long enough for the chlorine in your pool to have a chance to react with all of the toxins before they can build up. For that to happen, you’ll need at least two hours between each treatment- so plan accordingly!

Add Some Granular Chlorine

To use granular chlorine, you’ll need to add the granules to a bucket of water. Next, pour the pool shock treatment into your pool as well. Let it sit for around 35 minutes before rinsing the pool with clean water.

Granular chlorine is also a good idea because it can prevent or lessen the severity of possible corrosion problems in your pool’s water filter.

Add Some Algaecide

Algaecide is a chemical that has been developed to kill and inhibit the development of algae. One bottle of algaecide may treat up to 15,000 gallons of pool water, depending on the product. This will help in the prevention of future black algae blooms.

Run the Pool’s Pump

Black Algae: Run the Pool’s Pump

After giving the chemicals 24 hours to settle, turn on the pump for 24 hours. Then, keep it pumping for 8 to 12 hours a day, seven days a week for the remaining months of the season.

If your pool starts turning dark, run the pump immediately to prevent the discoloration of the surface of the pool. 

Brush More!

Black Algae: Brush the Pool

Keep brushing 2-4 times each day for several days to eradicate spores that may still be lurking. 

Clean Your Filter Once More!

You will need to thoroughly wash your filter again. This is to ensure that you already remove any residues from the sides of the pool.

Once again, DE and sand filters need to be backwashed and rinsed a couple of times to make sure you’ve removed any organisms that may cause another bloom.

Recheck for Black Algae

In some instances, if the algae in your pool are very persistent, you may see a black patch beginning to appear here and there.

Shock your pool again and continue with the brushing procedure at least twice a day until the black algae are totally gone.

How to Prevent Black Algae From Invading Your Pool?

The first line of protection is to wash your swimsuits, aquatic shoes, toys, and anything else that you may have used in a natural body of water before allowing it to even come into contact with your pool water.

Also, here are more tips on how you can prevent black algae:

  • Pressure wash decks and patio furniture since this can be a source of black algae.
  • Regularly pressure wash your screen and rail system.
  • Loosen bottom screen rails at low points to drain water
  • Remove all leaves that fall as soon as possible
  • Trim back overhanging plants and trees
  • Make sure you thoroughly wash rocks and water features that you’re putting in the pool


Now that you’ve finished all the hard work and would want to just relax by your pool, you can appreciate how critical it is to maintain your pool’s cleanliness. Every week, you should do routine pool care, such as brushing and vacuuming the pool, monitoring your pool’s chemistry, and cleaning the filters.

Remember to operate your pump regularly and clean all objects that contact the pool, including yourself and your family. Maintaining a clean pool does not have to be a tough chore, especially if you stay on top of the job.

These articles offer tips and tricks for keeping a swimming pool healthy. It will be helpful, I’m sure!

Photo of author

About the author

Brian Anderson

The rather dry pool world out there is in need of some passion to make it shine. With the help of my son Ruben and his wife Maria our mission is to help you create the favorite spot of your house - your pool.

Related Articles...

Leave a Comment