Black algae grows in difficult to reach areas like in the deep end, in corners, or around obstacles such as steps. It indicates poor circulation and poor sanitisation. Black algae are considered the most difficult algae to control, because it soaks into your pool’s pores. However, black algae are also the easiest to prevent.

To attack this bad boy, you’ll need an algaecide that contains a “penetrating” agent. That’s because most chemicals can’t penetrate black algae’s waxy coat.

But it’s essential, you start with the basics.

1. 1. Clean your filter. If your pool has black algae, your filter has it too.
   2. Scrub as much of the black stuff off the walls and corners as you can. This will also help break down the waxy layer and make it easier to treat.
   3. Shock your pool. Black algae istougher than other types of algae, so you may need to use a stronger dose.
   4. Add algaecide, with a penetrating agent, to your pool. This will help keep the black algae from growing back.
   5. Run your pool filter. Keep it running for at least 24 hours to ensure that the treatments and chemicals can circulate properly.
   6. Catch and eliminate future outbreaks  before they become an issue.

NB Health notice. Although black algae itself won’t cause illness, it can attract insects or harbour harmful bacteria like E. coli, which can make swimmers sick. So, don’t swim in a pool with black algae until you’ve eradicated it.