Brush all the surfaces inside your pool.
Removing black algae from pool walls.
This type of algae forms in a layered structure with the outermost layer protecting the lower layers.
During that 24 hour period while the chlorine level in the water is so high brush the surfaces at least two more times preferably three or four times to get any remaining black algae off the walls and floor of your pool.
Black algae can get into your pool several ways but one of the most common is from swimming suits that have been in the ocean.
Brush daily for a week with the proper brush for your pool paying special attention to algae affected areas.
For yellow and black algae it is a long process and cannot be achieved in a day or two but for green algae you may solve the problem in a matter of hours.
Black algae generally penetrate porous pool surfaces like concrete and gunite.
The first time you cleaned the filter was to get any live bacteria out of the filter.
Black algae are generally not an issue with smooth surfaced pools like fiberglass and vinyl.
Black algae have deep roots that work their way into.
Black algae is a thread like growth that develops on rough surfaces in swimming pools.
Those pesky little spores stick to the cloth and hop off in the pool the first chance they get so be sure to use bleach to clean them.
It appears as dark black spots on the walls and floor of the pool and is slippery to the touch.
Once these surfaces are infested with black algae it will take time and persistence to eliminate it.