In today’s guide, you’re going to learn how to finally get rid of that dreaded black algae in your pool.
Not only that …
But you’ll finally understand what black algae actually is, why it’s so bad for your pool, and how to also prevent it from ever coming back again.
Following the steps outlined in this guide has allowed my family’s swimming pool to remain mostly black algae-free for a while now.
What is black algae & why is it bad for your pool?
Black algae are living, growing organisms that, unless taken care of quickly, can overtake your pool and cause severe structural damage.
And it’s hard to get rid of because its roots grow into cracks in the cement and don’t like to let go. It also has a lot of protective layers that help it ward off the chlorine that should kill it.
Any algae, including black algae, tend to bloom in bodies of pool water with a high pH level, low chlorine, bad circulation and filtration and not enough chlorine. It will flourish in a warm pool with lots of sunny days.
>>Read: How to get rid of algae in your poolBecause of its appearance, black algae look a little frightening. I mean, we’ve all been warned of the health risks of black mold!
But it’s actually not harmful to humans all by itself (source). The health risk comes from the fact that algae can harbor harmful bacteria like E. coli. It’s important to note that not every dark spot in your pool is necessarily black algae, though.
Before you begin the lengthy process of removing it, it’s a good idea to identify whether or not the culprit is in fact what you think it is.
According to Pool Center, here’s how you can tell:
- 1The spots are black or blue-green with raised heads, not free-floating.
- 2The algae harbors in rough areas of the pool plaster.
- 3It doesn’t brush off the wall easily.
- 4The algae is found in pools even with proper filtration and sanitation.
- 5It’s not to be confused with mineral staining, which can discolor the surface (black), but won’t scrape off.
How to prevent black algae from growing in your pool
For all these reasons, the best cure is definitely prevention.
If you can stop it before it ever starts to grow, you won’t have to spend hours trying to get rid of it.
Here are our top tips for preventing black algae from growing in your pool.
1. Wash and dry swimming suits after swimming in the ocean
Black algae can get into your pool several ways, but one of the most common is from swimming suits that have been in the ocean (source).
Those pesky little spores stick to the cloth and hop off in the pool the first chance they get, so be sure to use bleach to clean them.
2. Maintain proper pool chemistry levels
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Regularly checking and regulating your pool’s chemistry, like pH, alkaline and chlorine levels will combat any infestation that may be threatening to erupt.
3. Run your pump and filter regularly
Running your pump for 8-12 hours every day will help filter off tiny spores that are too small to see.
4. Vacuum and brush your pool regularly
- STRONG: Metal backing provides enough strength to thoroughly clean pool walls
- FLEXIBLE: Designed with poly bristles to help reach the toughest corners
Brushing down the surface of the pool and vacuuming once a week will help keep all bacteria, algae and debris to a minimum. (Read: How to vacuum a pool)
5. Keep all pool equipment and pool toys clean and sanitized
Even if you have the cleanest pool in 9 counties, an infested pool noodle or floatie will muck up your summer fun before you know it.
6. Shock your pool every week
- Powerful chlorine shock treatment that is great for regular maintenance.
- Quickly eliminates algae, bacteria, and other harmful contaminants from your pool water.
Shocking your pool with an extra heavy treatment of a chlorine shock product should kill everything that shouldn’t be there. Doing it once a week will help you stay ahead of spores that threaten to bloom. (Read: How to shock a pool)
How to remove black algae from your pool
So, let’s say you forgot to read up on this before your pool got infested. Or maybe you’ve never had black algae before and the attack just caught you off guard!
Either way, no need to worry! You can get rid of it.
It will just take a little (or a whole lot) of elbow grease.
Follow these simple instructions and we’ll have you back in the water in no time.
Supplies you’ll need
- Pool Brush and Pole
- Pool Shock Treatment
- Algaecide
- Chlorine Tablets
- Granular Chlorine
11 steps for getting rid of black algae
1. Sanitize your tools
First you’ll need to sanitize everything you’re going to use so that you can make sure you’re not adding more algae to the pool.
You can do this by spraying and scrubbing it down with a chlorine solution.
2. Clean your filters
If there are algae in your pool, it is definitely in your filter, even if you don’t see it.
Be sure to follow your manufacturer’s directions for cleaning it, and remember that sand or DE filters will need to be backwashed and rinsed a couple of times.
3. Scrub the surface
Use your nylon brush to scrub the sides and bottom of the pool as many times as it takes to make sure all the pool algae are brushed away.
And, then brush it one more time for good measure!
Before you begin the lengthy process of removing it, it’s a good idea to identify whether or not the culprit is in fact what you think it is.
If you have a cement or natural element pool, a stiff or wire brush may be used to remove the protective layers of the algae.
And while a vinyl pool is not nearly as susceptible to algae, if you happen to notice an infestation, a softer-bristled brush can be used.
4. Scrub with chlorine tablets
- 99% Trichloro pool chlorine tablet that maintains a healthy pool
- Kills harmful bacteria
Scrub all the infected areas with a chlorine tablet. (You will probably want to wear gloves for this step.)
Now that you’ve brushed away the protective pool surfaces of the algae, the chlorine can penetrate it and get to the roots.
Break one in half and use the rough side to scrape the algae.
5. Shock your pool
Use a good shock treatment to blast away any bacteria and growths that might be lurking in the pool.
To do this, you will need a good super shock chlorine treatment.
You should follow the manufacturer’s instructions, but a good rule of thumb is to chlorinate your swimming pool water to 30 parts per million (ppm).
This will destructure the DNA of the algae so that it can be more easily removed.
6. Add granular chlorine
- CLEAR WATER FOR SAFE SWIMMING - Swimming in crystal clear water does not mean your skin has to suffer. The granular chlorine is 99% sodium diclor making a relaxing swim not as harsh.
- LONG LASTING - Dichlor resists UV light, lasting longer than other types of chlorinating supplies due to built in stabilizer for your swimming pool, hot tub, or spa.
Follow the manufacturer’s instructions for adding granular chlorine to your pool, being especially generous with it in areas where you scrubbed away algae patches.
If your pool has a dark surface, you may need to skip this step, as it could cause discoloration.
7. Add algaecide
- Safe with all pool and filter types
- Helps clarify pool water
Algaecide is a chemical created for killing and preventing the growth of algae.
One bottle of algaecide should treat 15,000 gallons of pool water. Use it accordingly.
This will help prevent future outbreaks.
8. Run your pump
After you have given the treatment 24 hours to settle, run the pump for the next 24 hours solid and then 8-12 hours a day every day of the season after that.
If you have a dark-colored pool, you will want to run the pump immediately to prevent discoloration of your pool’s surface.
9. Keep brushing
Brush your pool 2-4 times a day during the next few days to keep removing spores that may still be lurking.
10. Clean your filter
You will need to clean your filter again to remove any residue from algae that has been brushed away 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.
11. Check for algae again
If the algae in your pool are stubborn, you might notice a black spot starting to creep back in here and there.
If that’s the case, shock your pool again and continue with the brushing process at least twice a day.
Bottom line
Now that you’ve done all the hard work and would like to just enjoy your pool, you can see how important it is to stay on top of this task.
Every week, you should be doing regular pool maintenance such as brushing it down and vacuuming, checking your pool’s chemistry levels and cleaning out your filters.
You will also want to make sure to run your pump daily and clean any items entering the pool, including your humans.
Keeping your pool gunk-free doesn’t have to be difficult if you stay ahead of the chore.
Hi, I’m Matt Harper, the founder of poolcareguy.com, a site I started with one simple mission: to help people around the world clean and take care of their pools and hot tubs on their own, without the hassle.
I’m not a professional pool cleaner and don’t have any formal training, I’m just an average guy who loves hanging out by his pool and hot tub and taking care of it. After many years on the job, I’ve become quite good at it.
On this website I will be teaching you absolutely everything I know about pools and hot tubs.
We had our pool resurfaced with pebble fina. Within a few months a black stain started to develop, which never occurred in our old pool prior to the resurfacing. The stains were scrubbed off twice, but they would come back in the exact same places. A couple of weeks ago the pool was drained and acid washed by the contractor. A week later the black stains began to develop again in the same areas. The contractor said that the stains looked like they came from metal, but when we tested the pool’s water last week there was no metal. The pool has been professionally maintained on a weekly basis, but the stains are still developing. What are your thoughts?