Last Updated On: May 30, 2022
Are you frustrated seeing black spots in the corners of your pool? If wondering what it is, these spots are caused due o the growth of black algae in your pool.
Black algae usually set up in hard to reach areas such as corners of the pool and edges of the pool steps. These are the areas that you might have missed up brushing while cleaning the pool.
The growth of these black spots increases if you are not taking any preventive measures and may make your pool unsuitable to swim.
Here in this article, you can find the causes for the growth of black algae as well as a stepwise guide on how to get rid of black algae in pool.
What're Black Algae And Why Does It Grow In Your Pool?

The small black dots and blotches in the hard-to-reach areas of your pool are called Black algae. They are also seen on the floor and other pool surfaces. It is not actually a true algae, but a type of cyanobacterium.
These living and growing organisms may rupture your pool unless properly maintained. Although there are several reasons for their growth in the pool, improper circulation and filtration is the major reason for the outbreak of black algae.
The uncontrolled growth of black algae may impart a frightening appearance to your pool. it flourishes well in the warm water of the pool.
The major causes for the black algal growth in your pool are:
- High pH levels
- Low chlorine levels
- Poor pool maintenance.
- Bad circulation
- Improper filtration
How Do Black Algae Look Like in a Pool?

Black algae establish its growth in the pool as small black spots on the surface. The growth of these black spots makes the pool surface slimy and slippery. They flourish well on the cracks and crevices of the pool.
They impart no change in the appearance of the pool water as other algal formations usually do. Black algae belong to the group of blue-green algae and have a slimy layer and skeletal growths that make their body resistant to normal chlorine levels. Hence, they can’t be easily eliminated by shocking the pool.
How Can You Detect The Presence Of Black Algae In Your Pool?
Black algae appear as pin-head to quarter-sized black small dots. They are found in hard-to-reach corners and edges of the pool. These algae require a place to grab on to establish their growth and hence, flourish well in the cracks and crevises in the pool. Black algae are mostly seen in old and deteriorated pools with a rough surface for them to hold on.
Is Black Algae Harmful For Your Health?
Black algae don’t themselves cause any harm to human beings. They won't make you sick or hurt you. Swimming in a pool with black algae alone would not create any issues for your health.
But, they harbor the growth of bacterias that might cause diseases to human beings. Black algae catalyze and increase the growth of disease-causing microbes in your pool. Hence, it is recommended not to swim in a pool infested by black algae.
How To Remove Black Algae From Your Pool?
First of all, we can have a look at the list of tools and chemicals required to get rid of black algae in your pool. Later in the same session, you can find a detailed stepwise guide on how to get rid of black algae in pool.
Tools and chemicals required to eliminate black algae from your pool:
- Pool Brush: A hard bristle pool brush is essential to scrub away the algal bodies. Brushing the pool surface and filters is the most important and inevitable step in the process to get rid of black algae.
- Pool Shock: A good pool shock is essential to destroy harmful bacterial growths in the pool.
- Algaecide: An algaecide will kill the existing algae in your pool as well as prevents the future growth of the algae.
- Chlorine Tablets: You can use chlorine tablets to rub in the infested areas to scrub away the algal particles effectively.
- Granular Chlorine: You can use granular chlorine if you have a light-colored pool.
Stepwise Guide To Remove Black Algae From Pool:
Step 1: Sanitize Your Tools And Wear Gloves:
Black algae can spread via carriers. Therefore, before getting into the pool it is important to sanitize your limbs and tools. You can also wear gloves to avoid exposure to chemicals.
Step 2: Clean Your Pool Filter
Improper filtration is the major cause of the growth of black algae in your pool. The chances are high that you would find the filter of your pool clogged up. Clean the filter properly according to the manufacture's guide.
You might need to brush and rinse the filter several times to make sure that it is devoid of any algal particles.
Step 3: Scrub Away The Algal Growths
Black algal growths have many protective layers, a slimy layer, and skeletal growths. Hence, they are hard to scrub off and you should use a hard bristle brush for this purpose. They are mostly seen in hard-to-reach corners, make sure you don’t miss these hotspots.
Give importance to cracks and crevices of the pool as well. As a precaution, you can brush the pool a couple of times to ensure all algal growths are eradicated.
Step 4: Using Chlorine Tablets
Scrubbing chlorine tablets into the infested areas would help you to get rid of the algal particles in the deeper layers of the pool. The chlorine will penetrate into the roots and prevent further growth of the algae.
Step 5: Shocking Your Pool
Shocking your pool will help to destructure the algal DNA and destroy them more effectively and easily. In this case, to get rid of black algal growths, you can use three times the amount of pool shock you normally use.
Step 6: Adding Granular Chlorine
You can use Granular chlorine to maintain the chlorine levels and to destroy algal particles in the infested areas. Skip the step if your pool is dark-colored, as this would cause discoloration due to bleach deposition.
Step 7: Addition Of Algaecides
You can add an effective Algaecide from the wide arena of them available in the market. Add algaecides as prescribed in the instructions, don’t make the measurement more or less. Adding algaecide will destroy the existing algal particles as well as prevent further algal growth. Algaecides are more effective when applied in the mornings of sunny days.
Step 8: Wait For 24 Hours
Give your pool a time of 24 hours to settle up with all the treatments given. Let your pool get adapted to the changes. Run the pump for the next 24 hours.
Some Effective Tips To Prevent Further Growth Of Algae In Your Pool
- Don’t swim out in your pools directly after having a swimming session from the nearby oceans or ponds. The presence of algae in ponds and oceans is higher, and if you directly use the swimming pool, you might carry the algal particles into your pool as well. Therefore, wash and dry swimming suits well after swimming in an ocean.
- Maintain pool chemistry levels
- Proper and daily filtration will prevent the growth of black algae
- Vacuum and brush your pool at regular intervals. Invest on a quality pool cleaner for algae and dirt.
- Sanitize pool toys and tools before introducing them into the pool
Frequently Asked Questions:
1. What is the best algaecide for black algae?
Black Algaetrine is the beat algaecide available in the market. Black algae due to their protective, tough, and waxy coating require specially formulated algaecides. Black Algaetrine is such a type of algaecide especially formulated to treat black algae. It is composed of 3.07% of active copper. This algaecide is compatible with bromine, chlorine, and ozone sanitizers.
Final Words:
Black algae are not true algae, they belong to the class of blue-green algae collectively called as Cyanobacteria. Unlike other algae that infest pools, they are difficult to get rid of due to protective layers with skeletal growths.
However, you can check the detailed stepwise guide on how to get rid of black algae in pool in the previous section to eliminate them effectively from your pool.
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