How to Clean Black Algae in an Empty Pool

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Things You'll Need

  • Long-handled scrub brush

  • Vacuum

  • Hose

  • One gallon acid

  • One gallon water

  • Large can

You can cleaning black algae from a pool.

Many forms of algae can grow in pools. Green algae floats in the water of the pool and is the most common type. Yellow algae cling to the walls of the pool, normally in the shaded area. Black algae is the hardest to eradicate because it grows strong roots into the plaster of your pool walls. You see the heads of the algae on top of the plaster, and you must kill the roots. Killing the heads will not get rid of the black algae as it will simply grow more heads. You can eradicate black algae from an empty pool.


Step 1

Scrub the pool walls with a long-handled scrub brush. This loosens dirt, debris and black algae heads.

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Step 2

Vacuum the dirt and algae out of the bottom of the pool.

Step 3

Spray the pool walls down with a hose, wetting the entire area. Keep the hose running.

Step 4

Mix the acid wash. Pour one gallon of acid into one gallon of water in a large can. Do not pour water into acid, only pour the acid into the water.

Step 5

Pour the acid mixture down one section of the pool wall.


Step 6

Scrub the pool wall section with the scrub brush to distribute the acid.

Step 7

Rinse acid wash off the pool wall with the hose. Do not use a sprayer as it could back spray acid onto you. Allow the hose water to run over the walls without using a spray nozzle.

Step 8

Repeat procedure with each section of the pool wall.


You may repeat the procedure on the pool walls if you do not think all black algae is dead. Try using more acid and less water or scrub the walls harder when the acid is applied.


Wear gloves and goggles when working with acid. You may also want to wear a painter’s mask to keep from breathing acid fumes.


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