How to Kill Black Algae in Drained Swimming Pools

Fill the pool with fresh water and treat it with a copper-based algaecide, if the black algae outbreak is of minimum to moderate severity. These types of strong algaecide are often effective against lesser outbreaks of black algae. Scrub affected areas and treat them by shocking the water. (Apply very high levels of chlorine, Baquacil, or whatever sanitation chemical your system uses.) Finally, maintain consistent levels of your pool sanitation chemical and run the pump frequently to improve water circulation. If this fails to eliminate the black algae problem, proceed to step 2.

Give the pool a chlorine bath. This should be done by a professional pool cleaning service, as it requires high levels of chlorine. These levels are so high they could harm humans and badly damage pool liners or structures if used incorrectly. During a chlorine bath, pools are drained and high concentrations of chlorine are sprayed onto pool surfaces to kill black algae--both visible and invisible--deeply rooted in the walls of the pool.

Treat intensely growing areas of algae with chlorine treatments, which, again, are best executed by professional pool care technicians who apply strong doses of chlorine to the algae spots. The chlorine is scrubbed in with special brushes and tools to reach the hardest-hit areas of the algae attack.

Wash the pool thoroughly to remove all chlorine and algae from the environment. Drain the water or pump it out, as it's tainted and of no use to your pool.

Refill the swimming pool with fresh water and treat with chemicals regularly used in your pool.