- [Instructor] Now it's bad enough
to discover green algae in your pool,
but black algae?
Get ready, because you have some work to do,
and no one should swim in your pool until it's gone.
The good news is it's totally possible to kill black algae.
So here is a step-by-step guide
on how to get rid of black algae in your pool for good.
Check it out.
(upbeat old time rock)
(water splashes)
First, what is black algae, and why is it in your pool?
When you think of algae,
you probably think of something green.
Black algae is actually a bacteria called cyanobacteria.
It's also called blue-green algae,
but the bacteria can appear black.
So how does this kind of algae end up in your pool?
Well, someone probably swam in a natural body of water,
like a river, lake, or ocean,
and they didn't wash their swimwear afterwards,
bringing that black algae into your pool.
Next, is black algae harmful?
Yes, it actually can be.
Black algae can make anyone who uses your pool sick,
and it gets even more severe
if you accidentally drank infected water.
That's why it's important to identify black algae
as soon as you see it
and take immediate action to get rid of it.
But does what black algae look like?
Black algae looks like mold.
If you notice a bunch of tiny black dots
or big clumps of mold forming on your pool surfaces,
you may have black algae.
And they can sometimes look bluish green.
Here are a few ways to recognize black algae in your pool.
Number one, there are black or blue-green spots
and clumps with raised heads attached
to your pool's surface.
They don't float freely in the water.
Number two, it's on rough or porous surfaces.
Black algae seldom forms
on pools with fiberglass or vinyl liners.
It likes to grow in porous surfaces
like concrete, plaster, or gunite pools.
Number three, it doesn't brush off the wall very easily
with your regular pool brush or even a metal algae brush.
Number four, it can be scraped off the pool's surface,
even though it might take some extra work.
Pool stains, on the other hand,
could not be scraped off.
Number five, it shows up
even if your pool water is balanced, sanitized,
and filtered, because it enters your pool
from an external water source.
So how do you kill black algae?
Treating black algae isn't the same as treating green algae.
It actually takes a lot more effort and persistence.
But it is possible to kill.
So before you begin, you'll need the following supplies.
Test strips for liquid test kit,
an algae brush, chemical resistant gloves,
safety goggles, chlorine tablets,
a telescopic pole, filter cleaner,
and calcium hypochlorite shock, or Cal-Hypo shock.
And depending on the type of filter you have,
you'll need a backwash hose, filter sand, DE powder,
or a replacement filter cartridge.
Okay, let's get cleaning.
Step number one, clean the filter.
If you have black algae in your pool
you have black algae in your filter.
If you only have a little black algae,
you can just backwash your standard DE filters
or rinse your cartridge filter.
However, if you have a lot of black algae,
use filter cleaner rather than plain water.
You may also want to completely replace the filter medium
or cartridge to get rid of any bacteria.
Step number two, test and balance the water.
Use test strips or a liquid test kit
to test your pool water.
Focus on alkalinity, pH, and sanitizer.
Your alkalinity should be
between 100 and 150 parts per million,
with 125 parts per million being ideal.
Your pH should be between 7.4 and 7.6, with 7.5 being ideal.
And your chlorine should be between 1 and 3 parts
per million, or the proper range of whatever type
of sanitizer that you use.
Adjust your levels before moving on to the next step,
which is, step number three, brush the pool.
And I mean brush the pool
like you've never brushed before.
Brushing black algae loosens it
from the pool's surfaces and puts it into the water,
where chlorine will be able to kill it.
Use a stainless steel bristled algae brush to get
into those cracks and crevices
and really dig out that algae.
If you have a fiberglass or vinyl-liner pool
you'll want to use a nylon bristled brush,
but you're going to have to use twice as much elbow grease.
Step number four, scrub the black algae spots.
No matter how well you just brushed your pool,
you'll probably still see some black algae spots.
You'll have to scrub those by hand.
We recommend using chlorine tablets
to scrub the remaining algae patches.
This only works in concrete, plaster, or gunite pools.
Do not do this on a fiberglass or vinyl-liner pool.
Not only are you scrubbing off the algae,
you're also applying chlorine
which can start killing the bacteria.
First, you're going to want to put
on chemical resistant gloves and wear protective eyewear.
Two, break a three-inch chlorine tablet in half.
And three, hold it firmly
and scrub the black algae with the broken edge.
Don't worry if you don't get every speck of black algae
off the pool's surfaces,
because next you're going to step number five,
yes, brush the pool again.
There is a lot of brushing in your future.
I am sorry.
So give the pool another pass with the brush.
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Step number six, quadruple shock the pool.
Now that you've brushed as much black algae off as you can,
you need to kill everything that's floating in the water.
And a regular dose of shock won't kill black algae,
so we highly recommend using calcium hypochlorite shock.
Follow the manufacturer's instructions
to determine the correct dose for your pool's volume
and then multiply that by four for a quadruple shock
Check out our pool calculator video
if you need help figuring out your pool's volume
And here's a tip,
place all of your pool maintenance equipment you've used
in the shallow end of your pool to sanitize it
during the shocking process,
and remember to shock your pool at dusk or at night.
If you shock your pool during the day,
the sun's going to eat up most of that chlorine,
and it won't do its job correctly.
Step number seven, run the pump.
Run the pump for 24 hours to disperse the shock
and kill all that black algae.
We may come back to cloudy water,
but that's gonna be normal.
Step number eight,
yes, you guessed it,
brush the pool.
During that 24-hour period
while the chlorine level is at an all-time high,
you want to brush the surfaces,
ideally three to four times,
to get any remaining black algae off the walls and floor
and into that extra-chlorinated water.
Step number nine, clean the filter.
The first time you've cleaned your filter was
to remove any live bacteria.
When you ran the pump after shocking,
the filter probably accumulated bits
of dying black algae,
like it's supposed to.
So now simply backwash your sand or DE filter
or rinse your cartridge filter.
And to be on the safe side,
you can use a filter cleaner.
Step number 10, shock the pool again if necessary.
If you still see any remnants of black algae in your pool
after doing all of those steps,
you're going to want to shock it again.
This time you can just use a double dose.
Step number 11, run the pump again.
You can run the pump for 8 to 12 hours,
but to be on the safe side
we recommend running it for another 24 hours.
Step number 12, brush the pool.
Yup, I know, you saw that one coming.
Brushing is really the only way to get rid
of all of the bacteria off your pool's surfaces,
so you want to make sure it doesn't come back.
So do not skip the brushing.
Step number 13, test and balance the water.
After all that work,
your pool should finally be free of black algae.
Test the water and add the appropriate chemicals
as needed to bring all the levels back where they should be.
Step number 14, keep an eye out for stragglers.
Over the next couple of weeks,
keep a close eye on your pool
for any signs of black algae returning.
Even with all that shocking and brushing,
you may have missed a bit of bacteria
that will start to grow again.
If you do see a small spot reappear, brush it off,
scrub the spot with a broken chlorine tablet,
and then give your pool another normal dose of shock.
Finally, how do you prevent black algae in the future?
The first line of defense is to always wash your swimsuits,
floats, shoes, toys, and anything that you've may have used
in a natural body of water
before it goes back into your pool.
Swimwear should be washed in a washing machine
and all pool toys must be scrubbed and sanitized.
You can use a spray cleaner that contains bleach,
or dilute a tablespoon of bleach into a gallon of water.
And be sure to keep your pool properly balanced
and sanitized to prevent any future algae growth.
That means keep your alkalinity, pH, and sanitizer levels
in the recommended ranges at all times.
Run your pump and filter at least 8 to 12 hours a day
all season long.
Regularly vacuum and brush your pool.
Shock your pool at least every week.
Keep your pool equipment clean,
including skimmers, hoses, ladders, steps,
the diving board, slides, solar blankets,
and your safety cover.
And make sure anyone using your pool rinses off first.
If not, they'll be the ones doing all the scrubbing
and brushing if that black algae comes back.
Mark my words.
And that's it.
That's the long process
of how to get rid of black algae in your pool.
Good luck.
If there's a pool care topic you'd like us to cover
in a future video,
please leave a comment to let us know.
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if you found this video helpful.
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That's it.
Thanks again, and happy swimming.
(downtempo bass music)