Got Black Algae In Your Pool? Here’s How To Remove It In 5 Steps



Black algae. It’s not pleasant.

You and I both know that getting rid of it is far from easy, but by following these 5 quick steps, it’ll feel like much less of a chore.

In this article we’ll cover; what black algae is, what it looks like, why you need to get rid of it quick-sharp, how it differs from other forms of algae, and how to destroy it.

Black Algae Explained

If you’ve never experienced a black algae infestation before, this section is for you. You’ll need to know some basics if you hope to destroy it effectively. So, here we go.

What Is Black Algae?

The science-y bit:

Black algae are single-celled organisms that grow in large colonies. They are like other forms of algae, since they also contain chlorophyll, but are the most difficult to remove from swimming pools.

This is because they can protect themselves against their surrounding environment, making them much more resistant to your standard chlorine levels.

Why Is Black Algae Bad for Your Pool?

Black algae are SO unhygienic.

Letting it fester on the outer edges of your swimming pool is not a good idea because it harbours harmful bacteria like E. coli, which could result in swimmers getting sick, and it can also attract insects.

Would you want to swim in an unattractive, unkept and (frankly) gross swimming pool?

We wouldn’t either.

What Does Black Algae Look Like?

Knowing what to look out for will help you nip the spread of black algae in the bud a lot sooner, and in return your task will be much more straightforward.

Lookout for:

  • Blue-green or black spots that aren’t free-flowing (it’ll have a bumpy texture).
  • Rough patches or corners in your pool’s plaster – they like to attach to something.
  • How easily it brushes off. If it comes off easily, it’s not black algae.
  • Mineral staining. This is often confused with black algae as it can discolor the surface black and doesn’t scrape off. The keyword here is ‘surface’ though, so it’s not the same thing.

In short: if you spot any black spots, big or small, that are attached to the plaster in your pool, resembling a mould-like texture, you’ve got a black algae problem.

Removing Black Algae From Your Pool

Now you know you’ve definitely got it, let’s kill it. Be splash-happy and black algae free in 5 simple steps.

#1. Sanitize Like There’s No Tomorrow

If you or anyone you know has had a cheeky little swim in the contaminated water, make sure you ask them to wash their swimsuits as well as any floats or toys that have been in the pool.

If it can go in the washing machine, so much the better, this should kill the algae. Hand washing your swimmers might not be enough.

As for toys, floats and armbands, use bleach to sanitise them and scrub them with a brush just to be on the safe side. Do the same with any equipment you use for maintenance, including your filter.

Basically, anything that has touched or been in the pool will need a good clean.

#2. Have a Long Hard Look at Your Pool Water

Failing to monitor the pH levels of your pool could mean your black algae problem only gets worse.

This is why it’s important to make sure your pH levels are between 7.4 and 7.6, and your alkalinity is between 120 and 150 parts per million. Doing so will keep the chlorine working at maximum efficiency.

Of course, you’ll need a test kit like the one below to properly monitor everything.

LaMotte 2056 ColorQ Pro 7 Digital...
LaMotte 2056 ColorQ Pro 7 Digital...
  • Features a photometer which gives you a digital...
  • Water resistant housing and carrying case...
  • Tests Free Chlorine, Total Chlorine, Bromine, PH,...

#3. Scrub the Sides and Surface Until It Gleams

Make like your Auntie Debbie and brush that pool! Be aggressive. Black algae are stubborn, and you’ll need to put your back into it. Brush at least 3-4 times a day for as long as you can before wearing yourself out.

Buy a stainless steel algae brush, they are specially designed to cut into algae, making scrubbing a lot easier. Remember, this is going to be the difference between a hygienic and safe pool or repeat occurrences so buying the right tools to help you do a good job will always be a worthwhile investment.

#4. Make Pool Shock Your Best Friend

Pool shock is essentially a powdered form of chlorine used to combat harmful bacteria and other contaminants, including algae. It’s recommended to add three pounds for every 10,000 gallons of water. This will increase the chlorine levels up to five times the usual amount.

By ‘shocking’ your pool with higher chlorine levels, you help sanitize the water by boosting the ‘good’ chlorine, which is what will kill the baceria. Do it either first thing in the morning or at night, then run your filter for 24 hours a day until the black algae is a thing of the past.

#5. Repeat Step 3 (A Lot)

Responsible pool owners brush their pools on a regular basis. Following a black algae hit, scrub it down four times throughout the following day. Focus on the spot where the algae first appeared and work outwards from there.

Remember, black algae have deep roots that can penetrate the walls of your swimming pool. Just because you can’t see it, it doesn’t mean it’s gone.

Brush. Scrub. Repeat. Do so for about three or four days after the pool shock treatment then wait two or three days before shocking your pool again, with the usual amount. Then brush again until you feel confident it’s gone for good.

How to Stop Black Algae In The Future

After you’ve suffered through a black algae attack, you’ll not want to experience it again in a hurry. Here’s how to keep on top of it so it doesn’t happen again.

What Actually Causes Black Algae to Surface?

If you’ve recently swam in a lake or ocean (or any other natural body of water), then you’re at risk of brining black algae into a swimming pool. From bathing suits to furry canine friends, transferring the algae is easier than you realise.

Black algae love filthy water, and it doesn’t matter how much you keep proper chemical balance, if your filter isn’t operating well, you’re at risk. Check to see if your filter is clogged.

If it is, this could easily cause built up and encourage black algae to form. Cloudy water is another major tell tale sign, as it provides an ideal ecosystem to support black algae growth.

If you’re at the point where you can see black spots on the surface of the water, you’re too late, it’s taken hold.  

Good News, It Can Be Prevented – Here’s How:

The trick is to keep your water properly balanced and clean.

Be sure to:

  • Keep pH, alkalinity and sanitiser levels in the recommended range.
  • Run your pump and filter all day long (between 8 and 12 hours).
  • Clean your swimming pool thoroughly and regularly by brushing it, vacuuming it and hosing it down.
  • Add pool-shock once a week (1 pound per 10,000 gallons).
  • Maintain your pool equipment by keeping it sanitised – this includes any floats or toys that are likely to make contact with the water.

You could also shop around for some algaecide. This is a chemical formaula that attacks algae and prevents a reoccurance.

While chlorine is the all-round best method, this stuff is still worth trying. Unlike chlorine, it doesn’t get affected by mineral content, water temperature, sunlight or pH levels.

That’s a Wrap!

If you have an unfortunate black algae problem make sure you follow our 5 main steps, as listed above.

If you’re all about preventing a breakout, pay attention to your pool’s chemical levels and don’t ever shy away from your cleaning duties. If you do, you could be faced with a problem that just keeps bouncing back.

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In this article we’ll cover what black algae is, what it looks like, why you need to get rid of it quick-sharp, how it differs from other forms of algae, and 5 steps to remove it from your pool. #poolonomics #swimmingpool  #poolcleaning

Categories: Pool Care, Pool Problems