Black Algae & Swimming Pool Water Chemistry

This kind of algae can give you a real headache if not taken care of immediately. Unlike brown algae, yellow algae, blue-green algae, or green algae, this little guy forms layers and each layer forms a scab. Even when you have good pool water chemistry and practice excellent swimming pool care to a "T", it still might not be enough.

Beautiful Residential Pool

You need to get right on this because this bugger, if left on its own, will eat a hole right through your concrete.

Close-Up Shot Of A Black Algae Pool

Swimming Pool Algae Prevention

Properly balancing all of your pool’s chemicals and normal swimming pool care will greatly reduce, but may not eliminate the opportunity for getting green pool water, cloudy pool water, pink algae, and yellow algae.

Having your swimming pool chlorine, alkalinity, and hardness adjusted correctly is very important. Remember to brush and vacuum your pool because this will reduce the dirt accumulation and algae pores from sticking to the pool’s surface.

SAFETY FIRST

It’s easier, a bit safer, lighter in weight, easier to store, and 1 pound of granular chlorine equals 1 gallon (8lbs.) of liquid.

Chemical Help & Pool Cleaning Tips

I suggest you use granular pool chlorine, a.k.a. Calcium Hypochlorite, to shock your pool. This kind of pool chlorine has a pH level of 12.

Swimming Pool Chlorine

Now, anything over the pH level of 8.0 and you're only using about 25% of the chlorine, which means, you've lost 75% of the active swimming pool chlorine. When you add your pool chlorine, your pH will automatically go up, so get that pH down!!

You want to get rid of the dead algae.

So, What's Next?

Some may say that a pool algaecide specifically designed for black algae in swimming pools is a waste of time and money, but I've had some success with and without using a pool algaecide.

The algaecide you want to get is expensive, but I've heard it works pretty well. It's called a "poly quat". You could use this for your weekly pool maintenance.

First is to brush the spot(s) with a heavy duty wire brush. Doing this will loosen up the algae and help the chlorine penetrate the spot.

Remember, swimming pool black algae has layers so you want to get as many layers off as possible before adding the chlorine.

This is for a concrete pool (gunite swimming pool) and not vinyl swimming pools as this may tear your vinyl liner. Next, you'll want to apply your granular chlorine, or Calcium Hypochlorite, directly onto the black algae spot. Before you begin, make sure your pH is at minimum 7.0.

If you need to drain your pool, you can get chlorine tablets and go to work on the spot.

Add the pool chlorine around the perimeter of the pool and allow the filtration system Again, allow your system to run for another 24 hours. Vigorously brush your pool as often as you can. You have to get that black algae up from the roots.

Allow your system to run until the chlorine is down to 1.0-3.0ppm, normally about 2 weeks, maybe even less if you have a stretch of hot days.

What this does is brings your chlorine level up to an insane amount, about 50ppm, but this is black algae we're talking about.

Once the chlorine is down to a safe level and your swimming pool chemistry has stabilized, you may see some etching in your plaster from the pool algae.

You may need to get a sanding block from your local pool store and sand the areas where the black algae used to be.

Chart - Superchlorinate Your Pool
(Amount Needed to Reach 10 ppm)

Well, there you have it. I told you killing algae wasn't going to be fun, but if you have a pool with black algae, you gotta get nasty with it.

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Swimming Pool Algae From Black Algae
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Have A Question, Story, Or Comment?

If you have a chemical related issue, please give the chemicals readings, type of filtration system, what you've done or are trying to do, etc..

Chlorine
pH
Alkalinity
Hardness
Cyanuric Acid
Sand, Cartridge, DE Filter

Please explain your issue thoughtfully. By giving me all the details, it makes it much easier to answer your question and helps others that may have similar issues.

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