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How Do I Get Rid of Black Algae in My Pool?

By February 28, 2023May 10th, 2023Maintenance

Black algae is probably every swimming pool owner’s worst nightmare. Small patches of black algae stuck to your swimming pool surfaces signify that bacteria have already created colonies. Unfortunately, once this algae starts to multiply, eradicating it is challenging. You need expert advice and a sequence of sanitizing steps to eliminate black algae and turn your swimming pool into the beautiful aquatic space it should be. 

What Is Black Algae?

Black algae are technically single-celled organisms, but they grow in colonies. Like other algae, black algae contain chlorophyll. However, black algae also contains other compounds and bacteria, which is why it does not appear green. 

Typically, this bacteria lives in lakes, rivers, creeks, and ponds. It may find its way into your swimming pool even if you keep a good pool maintenance schedule. If untreated, it will take over your entire pool.

Unfortunately, black algae form a protective layer on the outside of their cells. This makes them more chlorine resistant and tough to eradicate once it enters your pool. So, you must go to extra cleaning lengths to remove it.

What Does Black Algae Look Like?

As the name suggests, black algae manifests as small black dots or patches on pool surfaces such as walls, steps, and corners. Upon closer inspection, it may look like these colonies have little heads popping up. You may also notice that these bacteria don’t float on the water but remain firmly hooked to the surface where they grow.

If you try to remove them by hand, you will notice that they are securely attached and are particularly difficult to remove, even with a brush.

Black algae has a preference for rough surfaces. Gunite and concrete pools are more susceptible to black algae infestation than fiberglass or vinyl pools.

You will find black algae lingering in the tiniest nooks of your pool, often hiding in the most unsuspecting places, like under the steps or in the corners. These are the most problematic spots to reach when you clean your pool. They should also be the first ones you hit when you notice black algae.

How Does Black Algae Get Into Pools?

The most common way for black algae to enter your swimming pool is through swimwear previously used in natural bodies of water such as lakes, creeks, and rivers.

Black algae naturally lives in these bodies. If you swam there and then jumped into your pool without washing your swimsuit, you may have unwittingly transferred black algae spores to your swimming pool. Anything else used in such natural bodies of water, like toys, floats, swimwear, or flippers may also carry black algae spores. Even your dog can carry black algae into the pool. 

We advise thoroughly cleaning all equipment before using it in your swimming pool. Accidents do happen, and it’s only human to forget to wash everything before using your pool. 

Although these bacteria are not harmful, they often encourage the development of other unhealthy microorganisms and bacteria, such as E. coli and cyanobacteria. Ingesting water infected with black algae is risky. So, if you have a black algae problem in your swimming pool, we strongly suggest you don’t swim in it until you can properly address the issue.

Why Is Black Algae Difficult to Remove?

All swimming pool algae can be hard to remove, but black algae is tough because it has two layers. For chemicals like chlorine to reach the inner layer and destroy the organism, it has to bypass the outer layer, which is quite complicated.

The other reason black algae is a formidable pool enemy is that it grows roots and attaches to surfaces. Even if you scrub the visible black algae layer, algae roots are likely embedded on the pool surfaces and will soon produce new black algae colonies.

How Do I Get Rid of Black Algae?

Getting rid of black algae involves a lot of scrubbing and pool shocking.

First, you must scrub the spots where black algae is developing thoroughly. This will destroy the outer layer of the bacteria.

Then you shock the pool at least twice to eliminate the inner core and exterminate the black algae colonies.

Clean Your Pool Filter

Your filter cleans and filters your pool water. That means if black algae is anywhere in your pool, it is also inside your filter. You should clean it with filter cleaner; otherwise, you will recycle black algae through the filter and back into the pool.

Brush the Infected Pool Surfaces

Take a steel-bristled brush and attach it to a telescopic brush. If your swimming pool is vinyl or fiberglass, use a nylon-bristle brush.

Start scrubbing all the affected surfaces. Your goal is to detach the black algae from any surface it has clung onto and let it float on the water. The pool shock you will later apply will kill the bacteria. You will need to scrub hard and reach even the tiniest specks of algae, as you need to eliminate all colonies. Any surviving specimens will start spreading again, and you’ll have to start from scratch.

If some spots require extra scrubbing, you can do so with a pumice stone or chlorine tablets. The advantage of scrubbing with chlorine tablets is that you will be detaching the black algae and exterminating it simultaneously.

Shock Your Pool

It is now time to shock your pool and sanitize it from all the floating black algae. To be thorough, you want to use three times the amount of shocking agent you normally use. It is best to shock your pool late in the afternoon so the sun doesn’t disintegrate the chlorine.

Run the Pool Pump for 24 Hours

You want the pool shock to circulate throughout the swimming pool, so you must run the pump for 24 hours.

While the pool pump is running, remove all lingering traces of black algae still clutching onto surfaces. The more you remove, the higher your chances of eliminating the problem.

Clean All Tools

You will need to clean all tools, brushes, and gloves you used during the brushing phase, or you will re-contaminate the water the next time you use them.

Clean the Filter

All the floating black algae has gone through the filter. You must now backwash the filter and clean it thoroughly, or you will recycle the black algae back into the pool.

Shock the Pool Again

The next step is to shock the pool once again, this time with the normal amount of shocking agent you use. To help the shocking agent circulate through the pool, run the pool pump for several hours.

Check Your Swimming Pool

As you have probably surmised by now, black algae is a fierce opponent. Check your swimming pool for any remaining black spots or any other signs that black algae is still lingering. If you notice black algae presence, you will need to repeat the whole process.

Balance Your Pool Chemistry

Assuming all black algae colonies have been eradicated, you will now need to rebalance your pool’s chlorine levels and overall pool chemistry.

Alkalinity should be between 100 ppm and 150 ppm, pH should be between 7.4 and 7.6, and chlorine levels must be between 1 ppm and 3 ppm.

Waterside Poolscapes for Your Black Algae Pool Problem

If you are stressed just reading all the necessary steps to eliminate your black algae problem, then you should call Waterside Poolscapes.

Our maintenance crews have dealt with black algae issues before and know exactly how to sanitize your swimming pool and restore it to its pristine condition.

Call us at 281-690-4810 and we will be with you right away to remedy your black algae issue!