Black algae: why normal shock does not kill it

Name: Rivera Pool Care
Address: Murrieta, CA, US
Telephone: (951) 383-9753
Price range: $$

Black or dark-teal spots that resist brushing are often cyanobacteria rooted into the pool surface. Its protective waxy layer blocks ordinary chlorine.

What pool owners should know

Physical disruption with a sturdy stainless-steel or hybrid brush is the crucial first step to break the organism's shield.
After opening the protective sheath, targeted high-chlorine treatments and localized brushing must follow.
Brushing twice daily for a week, along with elevated free chlorine and compatible algaecides, is often required.
Skipping days allows the algae to rebuild its protective coating and resist the chemicals all over again.

Rivera Pool Care takeaway: A clear pool is not proof the organism is gone. We treat the root system aggressively and consistently to prevent seasonal returns.