How to Get Rid of Black Algae in Your Pool.

Updated Jun 1, 2021

Pool Algae sucks! Especially Black Algae! And if you don’t maintain your pool water chemistry, it can and will creep up on you fast. Pretty soon, your pool water will become cloudy, and you will see a bunch of black spots, or mold-like stuff growing on the surface of your stairs, floor and walls in no time.


There are a few different ways you can approach things, but we figured you would want the fastest way to resolve the issue with the least amount of work. So, we came up with this quick an easy guide to get your pool back to crystal blue as fast as possible, just in case you don’t have a Smart Chemistry system already.

What is Black Algae?

Black Algae: This algae is also called, Black Beard Algae because of how it looks, and technical name is, “cyanobacteria.” It will appear in small, pinhead to quarter-sized, black dots or blotches around your pool surfaces. It appears like patches of dark hair, which is where the name came from. This is the hardest type of algae to kill and can come back if you don’t get it all out, including any roots that may be still clinging to your pool’s cracks and cervices.

Now that you have a basic overview black algae, let’s get into the best and fastest ways to treat it.

How do I Get Rid of Black Algae in My Pool Fast?

Smart SLAM! Method: This is, hands-down, the fastest way to get your Pool Algae under control. It can attack black algae quickly if done right.

It’s called Smart S.L.A.M. as in, “Be Smart, Shock, Level and Maintain.”

The idea behind Smart SLAM is to raise the chlorine levels high enough to kill any algae hanging out in your pool water.

This method will work for Freshwater and Saltwater pools. Yes, that’s right! So, please pay attention to get your pool water back on track.

Here’s what you need to do Prior to Smart SLAMing:

  1. Get Some Shock: Smart SLAM method requires calcium hypochlorite shock, AKA, “Cal Hypo” and not your typical chlorine tablets “tri-chlor” or “di-chlor”. You want the highest purity Cal Hypo without stabilizer, AKA, “CYA”. Tablets tend to come with CYA, which will build-up over time and affect chlorine reactivity.
  2. Get DPD Test Kit: Get yourself a DPD test kit to measure CYA levels You need to know how much stabilizer is in the water prior to starting, so you don’t have the stabilizer inhibiting your chlorine from doing its job. Levels should be no higher than 40ppm. If it’s higher, drain the water a little to dilute and refill as needed until the levels come down.
  3. Check pH Levels: You also need to get your pH levels between 7.2 to 7.8 prior to starting.
  4. Get a Brush: You will need a brush to get rid of any major debris prior to starting. Clear out the skimmer and pump baskets.
  5. Clean the Filter: Ensure you have a clean filter, so you don’t recirculate the black algae right back into your pool water. This algae type is notorious for getting back into your water. If you have black algae, your current filter most likely will need to be replaced, so get a replacement filter prior to Smart SLAMing

Now, that you have your prerequisites…

How to Smart SLAM Your Black Algae

  1. Run the Pump: Circulate the water for at least 24 hours prior to Smart SLAMing to allow your filter to capture whatever free floating black algae that it can.
  2. Clean the Filter: Clean the filter to remove any attached black algae. You can use the hose, filter cleaner or muriatic acid to soak the filter.
  3. Dose at Dusk: First and foremost, be sure to add the shock to your pool after the sun goes down to avoid UV rays and give the chlorine as much time in the water as possible. UV rays will destroy your chlorine so dusk and nighttime will ensure full potential of reactivity.
  4. Shock the Pool: You will need to dose the appropriate amount of shock to kill the black algae. Find out whatever the manufacturer of your pool shock recommends for your pool size, and multiply that number by the following to ensure you have enough shock in the water:

For Black Algae: Multiply by 4 (or 4 lbs of shock per 10,000 gallons)

  1. Scrub with Brush: Once you dose your water, take your brush and start scraping off the black algae from the walls, stairs, lights, etc. Now, that you have shock in the water, you want the algae to interact with the chlorine as much as possible, so brushing black algae off the surfaces will force it into the water and allow chlorine to start doing its job.
  2. Repeat as Needed: Wait 24 hours and repeat as needed until the water clears up.

– If you have black algae, you will most likely need to do several brushings to get it unstuck.

– You can also use large 3-inch chlorine tablets to hand scrub the tiny black algae spots that your brush can’t reach.

– And as mentioned, when things get under control, you can soak your filter in muriatic acid to kill any residual bacteria or simply replace the filter.

– Be sure to always wear protective gloves, goggles, etc when scrubbing anything.

How do I Prevent Black Algae from Growing?

There are three focus points you always want to remember to prevent black algae from coming back to haunt your pool. 1) Pool Chemistry, 2) Pool Circulation, and 3) Pool Cleaning… the Three C’s of Pool Maintenance.

Pool Chemistry

Maintaining pool chemistry will be about 90% of your pool maintenance battle plan!

Pool Circulation

Maintaining pool circulation will be the next 5% of your pool maintenance battle plan! Stagnant Water is the Enemy!

There are two huge reasons you will want to circulate water…

–  Filtration:

You need to circulate water through the filter so dirt, pollen, and any other nasty particles that happen to land in your pool are removed and nothing messes up the pool water.

– Sanitation:

You need to circulate sanitizer (chlorine) throughout the pool to kill microorganisms. If any microorganisms get into the water, they can create problems with the water chemistry, algae can start forming, or worse… the water can become toxic to swimmers.

The great thing about these first two C’s… if you handle Pool Chemistry and Pool Circulation, then, the last “C” – Pool Cleaning, is a piece of cake.

Pool Cleaning

Maintaining a good pool cleaning schedule will be the final 5% of your pool maintenance battle plan!

Some things you just can’t get around, such as monsoons, haboobs, dust storms, bush and tree leaves falling into your pool.

So, every so often, you will need to scoop, skim, brush and dump stuff out of your pool.

Debris, if left unchecked, can block the flow of the skimmer and clog up your pool filter.

In sequence, we recommend…

a. Dump Skimmer Basket

Clear the suction path so the vacuum and pumps can do their jobs. Most floating debris ends up in the skimmer basket. Staying on top of dumping the baskets will help reduce the work that your pool filter needs to do.

b. Vacuum the Pool:

The heavy debris in the pool should be settled if you are just starting your cleaning process and it should be concentrated toward the bottom.

c. Brush the Pool:

After vacuuming, start brushing to knock the stuff off the walls, stairs, etc so your filtration system can eat them up like candy.

d. Run the Pool Pump:

Your pump needs to run long enough to fully circulate the water at least once.  We have a pretty extensive article to describe everything you need to know about running your pool pump.

What is the Minimum Circulation Required for my Pool?

And there you have it… Three C’s of Pool Maintenance!


Anyways, we hope this guide was useful. We have been maintaining pools for some time now and found that the above recommendations should keep you on the right track for getting rid of that pesky black algae.