Learn More › Black algae in a pool is not just unsightly. Although it isn’t harmful itself, it can spread rapidly and harbor dangerous bacteria, like E. coli, that can make swimmers sick.

Q. I am a winter resident in Ft. Myers, Fla., and live the rest of the year in Massachusetts, where I have a vinyl 20-by-40-foot in-ground swimming pool. Last spring when I removed the cover, I not… ...

Cornerstone comes in, and treats the pool, bringing it from black to blue again. Dirty swimming pool. ... If a job requires algae removal or a slight buildup on walls, ...

Question: Is it safe to swim in a pool with black algae?Answer: It won’t hurt you, but if you see black algae, it is time for an aggressive treatment before the problem gets out of control and ...