For those who have experienced black algae you’ll know just what a headache it is to remove, you think the problem has been resolved only to find the black algae returns with a vengeance! Typically black algae appears mid-summer and tends to stay around for most of the season, it is particularly impacted when the swimming pool is located in unshaded locations, in direct sunlight.

You’ll predominately experience black algae in tiled or marbelite finished surfaces (liner pools tend not to suffer from black algae), the black algae grows on the grout in between the mosaic tiles and sporadic areas of marbelite surfaced swimming pools. There is a cure to this problem, and by following the steps below will help ensure black algae is a thing of the past


  • Lower the pH of the water to 7.0 – 7.2 – use OPC pH Minus and monitor readings with OPC Pooltester. If you are struggling to reduce the pH check the Total Alkalinity (TA), if this is above 180ppm lower the TA reading with OPC TA Alkalinity Reducer. It is essential to reduce the PH so that the hard waxy coating protecting the black algae spores is softened to enable effective penetration of the treatment chemistries.


  • Brush the affected area with a stiff pool brush, a wire pool brush is ideal but ensure you check the suitability of the surface before using a wire pool brush




  • Once the above process is complete undertake a full backwash on the filter to remove pollution from the filter media.



  • The black algae should now disappear, don’t forget to regularly shock dose the water (weekly) and top up algaecide levels, letting the free chlorine, pH and algaecide levels to drop may invite the black algae back.


Remember, prevention is always better than cure, maintain free chlorine levels between 2 – 3ppm and pH levels between 7.2 – 7.4 and regularly add a quality algaecide such as Klearpool Long Life Copper based Algaecide, Summerguard Copper Algaecide or Summerguard Copper Free Algaecide

*Use biocides safely.  Always read the label and product information before use.