Black Algae Treatment Tips!

Black algae is a plague of the pool industry. Like the black death in Europe well, probably not that bad, but still, it is sometimes death to the pool, especially a large outbreak. There are some ways to cure and treat black algae and I will outline the steps here for you.

Chapter Marks:
00:00 Intro
01:06 ID Black Algae
03:07 Spreads Quickly
04:49 FC to CYA Formula
06:41 Treatment

First, you have to find out if it is black algae or maybe something else like copper staining. The best way to accomplish this is with the use of a 3” trichlor tablet. If you can reach the spot you can rub the tablet over it and if the spot lightens or disappears it is more than likely black algae. If you can’t reach it or if you have a lot of spots on the walls of the pool, a tablet holder is a great option for you.

This Algae Gone Tablet holder is a great tool:
https://amzn.to/3y3bdH7

After you confirm it is black algae now we must treat it. Since the heads on black algae act as a protective barrier, brushing off the heads is step one. A good 5-6” Stainless Steel Algae brush is a good option. I like the A&B brand but any 6” SS brush will do. This is time-consuming and requires lots of manual labor.

Next, you want to raise the chlorine level to very high levels. The go-to chemical in the past was HASA Algi-ban but this has been in short supply. It is also a bit dangerous to use as you can burn the plaster. You have to just sprinkle it lightly over the black algae and make sure it does not pile up anywhere on the plaster. You may want to just use a 20 lb bucket of Cal-Hypo and broadcast that in the pool over the spots (make sure the pool pump is off). Let the chlorine settle over the black algae for a few hours and then run the pool pump as long as possible after. Raising the chlorine to 50 ppm for 3-5 days is an effective treatment method.

Black algae are also killed by copper. So a good copper algaecide will be effective, slower than the chlorine bombing but effective. A PoolRx unit works great because the copper in there will eventually eliminate the black algae. Algatec is Synergy Algaecide for Green, Yellow and Black Algae by Easy Care and it is also effective against black algae. Just note that the treatment is very slow and it will take 3-4 weeks before you start to see the black algae disappear.

A combination of both methods works best. Raise the chlorine to 50 ppm for 3-5 days and then when the level drops back down to 5-10 ppm use the copper algaecide, Algatec by Easy Care, or the PoolRx to eliminate the black algae.

In the case where the pool has more black algae than white plaster showing, a full drain and chlorine wash is the best solution. Note that you should observe the following cautions:

Don’t drain the pool water into the street or gutter as the city may find you
Don’t leave it empty for more than 24 hours-48 hrs
Never drain a pool when the air temperature is over 100 degrees
If the plaster has chips and cracks note that after refilling the chips and cracks may become larger

After draining use a chlorine and water mix of 50/50 and pour it or spray it over the black algae. This is called a Chlorine Wash. Sometimes you will need to power sand the spots out or use a pressure washer to remove the black algae from the surface after the Chlorine Wash.

Black algae is treatable and a great resource is this book:

How to Get Rid of Swimming Pool Algae by Rudy Stankowitz
https://www.amazon.com/dp/B08W7SH8PJ/ref=as_sl_pc_qf_sp_asin_til?tag=swimmingpooll-20&linkCode=w00&linkId=af0c5091232433ab3079b9da506c3549&creativeASIN=B08W7SH8PJ

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