How To Remove Black Algae Stains From Pool Walls?

One of the most difficult problems to solve in our swimming pool is probably the appearance of black algae in the pool, because of how complicated it is to clean them.

The reason why it is very complicated to eliminate the black algae of the swimming pool is that these can be encrusted and extend their roots in the walls, especially on the porous surfaces of the joints of the swimming pool.

To eliminate black algae from swimming pools we must take very radical and strong measures since this plague is very easy to spread in the waters and generally comes from the infected bathing clothes of the sea.

How To Remove Black Algae Stains From Pool Walls

Getting Rid Of Black Algae Stains From Pool Walls

Black alga is a real nightmare for pool owners, and what’s more: it is one of the most difficult algae to get rid of. If you have black algae in your pool, here is the best way to get rid of it quickly and for good!


Step 1: Scrub the pool walls

Get ready to thoroughly scrub the pool walls as you’ve never scrubbed them before!

If you have a vinyl liner, use a nylon brush.

If you have a stone pool, use a stainless steel brush.

As you scrub, the black algae will peel off the pool walls and float in the water, where it will be removed in the next stages.


Stage 2: Keep scrubbing (with a wire brush).

Again, if you have a vinyl liner, skip this step. If not, continue scrubbing intensely to remove the last traces of black algae that resist on the walls. Use a knife or wire brush if necessary.

Remember that we want to get rid of ALL areas where black algae have settled.


Step 3: Clean the filter

If you have black algae in your pool, it is almost inevitable that you will also have it in the filter. If you have a cartridge filter, it is time to think about changing it, otherwise, you can opt for a complete chemical cleaning.


Step 4: Test and balance your water

Every time you want to treat the pool water, test and readjust the pH and TAC to their ideal levels:

TAC: between 100 ppm and 150 ppm.

pH: between 7.2 and 7.4

If levels are too high or too low, readjust before proceeding.


Step 5: Apply a shock treatment (x4)

If you thought yellow algae were difficult to remove, black algae are even worse! Now that you’ve descaled the algae from the walls, it’s time to remove it.

Follow the manufacturer’s instructions to determine the correct dosage depending on the volume of the pool and multiply the result by 4!

We advise you to use calcium hypochlorite for this treatment. And above all, apply the treatment at night (not because the bacteria are asleep, but because chlorine is less effective in sunlight)!


Step 6: Turn on the filter for 24h

Now that you have finished the treatment in the pool, let the filter pump run for at least 24 hours. Don’t worry if the water gets cloudy, it’s completely normal.


Stage 7: Scrub again!

While the filter is working (and at least 8 hours after the treatment), continue to scrub the areas where you see any traces of algae. Do not hesitate to spend as much time as necessary and repeat the process several times!


Step 8: Clean the filter again

The first time you cleaned the filter was to remove the black algae present in it. This time, we want to get rid of the dead algae. There is no need to do a chemical cleaning, a simple backwash will suffice. If you have a cartridge filter, a rinse should suffice.


Stage 9: Reapply a shock treatment

This stage is only a precautionary measure, but if you have gotten this far, you will have understood how difficult it is to get rid of black algae.

So as not to take any risks, make sure you have got rid of all the black algae with a new shock treatment.

Doubling the dosage this time is sufficient, there is no need to quadruple it as in the first treatment.


Step 10: Turn on the pool pump

After this second shock treatment, you can turn on the filtration pump again for at least 12 hours (24h if you really don’t want any risk).


Step 11: Keep scrubbing

Even if you don’t see any more algae, don’t skip this step, and scrub the pool walls again! Black algae are microscopically embedded in the walls, which is precisely why they are so difficult to remove.


Step 12: Re-test and re-balance the water

After so much shock treatment, be sure to check the correct water balance. Don’t worry if the chlorine level is high, as it will drop naturally after several days.


Read: Can You Swim In A Pool With Black Algae


An Alternative Method Of Removing Algae Stains From Pool Walls

The first thing we need to remove algae is a good brush, which has a good hardness. The first step for the elimination of algae is the disinfection of all the accessories that we use to bathe.

These complements can be balls, toys, floats, swimsuits, goggles, swimming caps, etc. Most of the time we have algae in the pool it is probably because our swimsuit or bathing equipment has had contact with algae from the sea.

It is important to clean all these items after using them at the beach and even disinfect them with bleach.


Water chemistry plays a fundamental role in the appearance of algae in the pool. It is advisable to make sure that the pool water has a pH at a suitable level, from 7.4 to 7.6, and with alkalinity of about 140 ppm. This measurement should be done both before and after the algae removal treatment of the pool.


We know that it can become a nightmare following the step that we are going to explain to you for the elimination of the algae, nevertheless, it is very advisable to realize an exhaustive brushing of the walls of the swimming pool.

To do this we will need, as previously mentioned, a good brush and rub very hard. It is essential to brush very hard and insist that the algae come off.

The following step will be to make a shock treatment to disinfect the swimming pool and eliminate the annoying black algae. For this, we will use a larger amount of chlorine to make sure that all the algae disappear completely.

In addition, it is very important to run the filter for at least 24 hours, to make sure that all the dirt is properly removed.


Final Thoughts

You’ve done it! You’ve eliminated the black algae from your pool! However, be vigilant over the next few weeks: if you notice even the slightest reappearance of algae, apply the shock treatment immediately and then start scrubbing again! You may have missed a tiny area where they were hiding the first time.

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