Can You Swim In A Pool With Black Algae

You expect to see certain colors in your pool. Blue, of course, since most of the pool liners and walls are blue. White is the color of most of the plaster features, such as the steps.

Silver of the handrails and stair treads. But black? That’s a sign of trouble. Big trouble.

Can You Swim in a Pool With Black Algae

It’s bad enough to find out your pool is infected with green algae. Fortunately, that’s usually pretty simple to address.

But if you discover black algae in your pool, get ready because you have some work to do to get your pool back to normal. And for your safety, no one will be able to swim in it until you do.


Can You Swim With Black Algae In The Pool

Swimming in water infected with black algae can be enough to cause illness. But the likelihood and severity of illness increase if you accidentally drink infected water.

You should hold off swimming if you have black algae in your swimming pool. It may not be safe and may cause health issues. Treat the algae by super chlorinating (shocking) it and scrubbing the algae before swimming in the pool.


Why Do You Have Black Algae in your Pool?

Simple. Someone swam in natural water like a river, pond, lake, or ocean, then didn’t wash the swimsuits and then used the same swimsuit in your pool.

It’s less likely, but black algae can also show up to your pool via airborne spores.

Now what? Well, the first step to getting rid of black algae is to understand what it is, because guess what? It’s not algae at all.


What Are Black Algae?

True algae are aquatic plants that belong to a group that includes everything from single-celled organisms to algae. That’s why when you think of algae, you think of it as something green, it usually is.

Like most plants, green algae contain chlorophyll, the pigment that gives it its green color.

Chlorophyll is also the substance that allows a plant to photosynthesize, the process by which the plant uses light to synthesize food from carbon dioxide and water.

What we call black algae is actually bacteria. Specifically, a cyanobacterium, which refers to blue-green algae, hence the cyan part of its name.

So, if black algae are cyanobacteria, which are blue-green in color, why are they black?

Cyanobacteria contain chlorophyll, which contributes to their blue-green color.

But it may also contain other water-soluble pigments that, when combined with the blue-green pigment, make the bacteria appear black.


Read: Can You Swim In a Pool With Mustard Algae?


Is Black Algae Harmful?

In a word, yes. It can be. However, the emphasis on this danger is usually placed on blue-green algae.

Cyanobacterial blooms in natural bodies of water can kill other organisms and animals living in that water by blocking sunlight and accumulating oxygen and other nutrients.

This is not something you need to worry about in your pool.

But cyanobacteria also produce cyanotoxins, which are among the world’s most powerful natural poisons. They can make you, your pets, and any other animals that might find their way into your pool sick.

If you have black algae in your pool, and your kids accidentally swallow the pool water while they’re swimming laps, they could experience everything from nausea and stomach cramps to liver damage.

And have you ever seen your dog take a drink from the pool? They are in the same danger of getting sick if the water is infected with black algae.

You must be able to identify black algae as soon as it appears and take immediate action to get rid of it.


How To Recognize Black Algae In Your Pool

It’s actually not algae, it’s cyanobacteria – no wonder these things are so hard to kill! It’s like a chameleon!

Seriously, if you notice something starting to form on the surfaces of your pool and it looks like a bunch of little black dots or large clumps of mold, you may have black algae in your pool.

And because they are cyanobacteria, those clumps may actually look more blue-green than black.

Also, black algae rarely form in pools with fiberglass or vinyl liners. It’s more in plaster or gunite pools because those are porous surfaces that the organism can actually latch onto and even “grow roots” beyond the surface.


Some other ways to recognize black algae in your pool:

  • Black or blue-green spots and clumps have raised heads and are attached to the pool surface. They do not float freely in the water.
  • Settles in areas where the pool surface is rough and they can actually grab.
  • It is not easily brushed off the wall with the pool brush. Sometimes even with an algae brush.
  • It can be scraped from the pool surface, although you will need elbow grease because it is a very expensive procedure. Pool stains can not be removed.
  • You can find it even if you are vigilant about keeping your pool water balanced, sanitized, and filtered.
  • Recognizing it means you can take the right steps to get rid of them because treating black algae like green algae won’t work. You’ll need to take out the big guns.


Read: Can You Vacuum Algae Out Of A Pool?

How To Kill Black Algae

Simple green algae are pretty easy to kill because it’s a plant, and anyone who doesn’t have a green thumb can attest that you can kill a plant just by looking at it the wrong way. Or is it just us?

Anyway, the fact that the black algae in your pool are actually bacteria is what makes it so tough and hard to kill. And you thought it was just a movie.

The good news is that it’s not impossible to kill them. You’ll just need a little more effort and persistence on your part.

Before you begin, gather all the materials you’ll need:

  • Backwash hose (if necessary).
  • Filter cleaner
  • Filter sand (if needed)
  • Dust (if needed)
  • Replacement filter cartridge (if needed)
  • Test strips or liquid test kit
  • Algae brush
  • Chemical resistant gloves
  • Protective goggles
  • Chlorine tablets
  • Chlorine tablet holder
  • Telescopic pole
  • Calcium hypochlorite shock


Be sure to stretch before you start because you’re going to get a good workout.

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