How To Get Rid Of Black Algae In Your Pool

What Is Black Algae?

Black algae are small living organisms that penetrate porous pool surfaces like gunite and concrete. The black algae roots grow into the cracks of the plaster where they lock in and don’t like to let go.

With an above-ground pool, you will get the black algae that start to form together as clumps in the water. The pool cleaning process will be very much the same for both types of pools.

There is an effective way to treat black algae and eliminate them from your swimming pool water. The problem with black algae is that it has roots that grow into the cracks of the inground pools plaster.

What Causes Black Algae In Pools?

Black algae mainly come from dirty pool water. When the filter or skimmer baskets are clogged, or the pump is not being run every day for long enough periods. Not brushing the pool enough. You should brush the pool at least once every three days. Also, black algae will grow in pool water with a high pH level and a low chlorine level. 

Is Black Algae Dangerous Or Harmful To Humans?

Yes, Black Algae can cause a person to get sick and cause illness. The black or bluish-green spots will be a deterrent to any swimmer.

Swimming in water infected with black algae can be enough to cause illness. The probability and severity of illness are increased if you accidentally swallow the infected water.

You could experience anything from Stomach Cramps to Nausea and possibly Vomiting. Be careful of your pets too. Make sure they do not drink this water either as they will also get sick.

This is what I have been able to do to treat black algae and stop it from returning and the pool chemicals that I have used.

How To Get Rid Of Black Algae In A Pool

Before you begin. These are the Supplies you will need.

1. Clean Your Pool Filters

When you have black algae in your pool, you definitely have black algae in the pool filter. If you have a DE or a Sand filter, I recommend that they are back washed and rinsed at least twice.

If you have a cartridge filter and the black algae infestation is bad then I suggest removing and rinsing the filter with filter cleaner or even replacing the filter.

2. Brush The Pool Walls And Floor

If your pool surface is gunite or concrete. Then I suggest using a very stiff-bristled brush or a stainless steeled bristled brush.

If your pool surface is fiberglass or vinal. Then I suggest using a soft-bristled pool brush.

Now that you have chosen a suitable brush for your pool surface, its time to get brushing. Now you need to brush the black algae from the sides then the bottom of the pool.

What this does is loosen the black algae from the pool wall and floor surfaces and puts it into the water.

This is where the pool shock will take over and kill the black algae.

Remember the black algae is very stubborn and grows into the cracks and tiny crevices of the pools plaster. That’s why, if after the first round of brushing you still see some black algae spots left. Brush for the second time.

If after the second round of brushing there is still black algae spots then its time to use the chlorine tablet.

Put on your chemical-resistant gloves and eye goggles. Break a 3-inch chlorine tablet in half and fit it into a Pentair Algee-Gon 3 Inch Chlorine Tablet Holder with the broken tablet edge facing outwards. Attach a pool pole to the chlorine tablet holder if necessary.

Now brush those areas that were not removed by normal brushing with the chlorine tablet. What the chlorine tablets do is apply chlorine directly onto the black algae which penetrate into the roots of black algae which start killing them off immediately.

3. Shock The Pool Water

Now that all the black algae are mixed and floating in the water it is time to shock treat the pool water. I highly recommend these pool chemicals, calcium hypochlorite shock to kill the black algae. Or you may use granular chlorine.

Follow the manufacturer’s instructions to determine your pool’s volume for the correct amount of chemicals needed for shock treatment. Then either increasing the shock level of treatment to 30 ppm or times the amount by four.

If you are not too sure how much water your pool holds?

Then you can use our pool volume calculator to work it out.

It’s a good idea to put all the pool equipment you used eg tablet holder, algae brush, pool pole leaf skimmer, etc into the shallow end so that they can be sanitized during the shocking process.

Remember it’s best to shock your pool at sunset or at night. If you shock your pool during the day most of the effects can be lost due to the sun eating away at the chlorine before it has a chance to kill the black algae.

I would recommend adding 1Quart of Algaecide. This chemical kills and prevents algae from growing again. This helps prevent further outbreaks of black algae.

4. Run The Pool Pump

To get the shock treatment chemicals to mix with the black algae you will need to run the pool pump for the next 24hours continuously. The pool water may turn cloudy, but that’s normal.

Continue at regular intervals to brush any remaining black algae off the walls and floor of your pool. I had to brush another 4 times to make sure there were no remaining black algae spots.

5. Re Clean The Pool Filters

When the pool pump is running all that black algae is going to be sent through the filters. You will have to clean the filters again after the 24hour pump cycle to get rid of the dead black algae.

Rinse with water or use a cartridge cleaner for the filter when dealing with black algae. It also depends on the severity of the infestation that you had.

The Sand and DE filters will need to be back washed and rinsed well to make sure all black algae spores are gone.

It is possible that the filters might need to be cleaned for the 3rd time after 48hrs have passed.

6. Check For Black Algae And Shock Pool Again If Necessary

After the initial shocking of the pool. Running the pump for 24hrs and cleaning the filters. If you still see black algae on the pool surfaces, shock treats the pool again.

When you shock the pool this time only double the recommended dose. Run the pool pump for another 24hours. Continue with the brushing. At least twice a day.

7. Test And Correct The Balance Of The Pool Water

After about 2 days your pool water should be free of all black algae. Using the correct test kit, test the water PH and Total Alkalinity chemistry levels and add the appropriate chemicals as needed to bring all the levels back to where they should be.

8. Now That The Black Algae Has Gone

I am sure you are exhausted after that job. I never want to do that again.

Regular pool maintenance every week is so important. Such as cleaning out the filters, running the pump, testing the water chemistry, vacuuming the pool, brushing the pool, etc.

This little bit of work when the pool stays clean is much better than a 2day nightmare. A clean pool is easier to maintain than a dirty pool.

Weekly maintenance keeps your pool safe for your family, friends and pets.