How to Clean Black Algae Stains From the Bottom of My In-ground Pool

As with most pool owners, you might think that all algae is the same --- regardless of color. However, the color of your pool's algae does affect the difficulty in eliminating it from a pool. Black algae are the most difficult algae to control and eliminate from your in-ground pool. Black algae contain an outer surface called polymucosaccharide. This outer surface acts as water repellent and prevents chemicals from entering the nucleus. However, with the right chemicals and care, you can remove black algae.

Poly quat algaecide
Granular pool chlorine
Pool brush

Instructions

- 1
  Adjust your pool's pH to 7.0 to 7.2, the alkalinity to 85 to 100 ppm and hardness to 150 to 250 ppm. This will give your pool the correct environment in which to neutralize the black algae.
- 2
  Add a poly quat algaecide to the pool weekly. A poly quat algaecide will break through the black algae's water-repellent outer surface, allowing the other chemicals to destroy the exposed algae membrane.
- 3
  Use granular pool chlorine to shock the pool. Granular chlorine has a pH of 12, which is ideal for killing black algae.
- 4
  Scrub the bottom and side of the pool, using a pool brush. Skim out the loose debris.
- 5
  Run the pool filter every day, and do not turn it off until you've removed all the black algae.
- 6
  Backwash the pool twice a day to remove black algae from the filter.

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