Black Algae: The Pool Owner’s Nightmare

Black Algae: The Most Difficult Pool Contaminant Black algae is not technically algae but a cyanobacteria that forms a highly resilient protective layer (a biofilm) over its colonies. It typically appears as dark black or deep blue-green spots that embed themselves into the plaster surface, often in rough spots or corners. Unlike common green algae, black algae is highly resistant to standard chlorine doses. Treatment is aggressive and requires specialized effort: 1) We use a stainless-steel brush to scrub the patches vigorously, breaking the protective biofilm. 2) We then target the area with concentrated, granular sanitizer or a specific black algae treatment chemical to penetrate the colony. 3) The area is brushed again, and the filter is run continuously. Because black algae roots itself deep into the plaster, it often requires repeat treatments and careful monitoring. DIY attempts usually fail and only waste chemicals. Shipwrecked Pools has the specialized training and equipment needed to eradicate this persistent problem and prevent its return.