Biofilm is used to describe some different growths that are bacterial in nature. The two most frequently seen in pools and spas are commonly referred to as “Pink Slime” and “Water Mould”.

Pink slime:


Pink slime, also called Pink or Red Algae, is not algae at all. It is a mixed growth of bacteria and other micro-organisms and can also be clear to whitish in colour. It is a non-pathogenic slimy pink growth.

Pink slime tends to grow in areas of poor circulation and on plastic. Some common areas of pink slime build-up in pools are underneath ladder treads, inside the skimmer baskets, on skimmer doors, on return fittings, behind the light niche, and in cracks and crevices around steps and seams. tile grout, on return fittings and skimmer doors and baskets.

Water mould:

Water mould, also referred to as Toilet Tissue Syndrome, is a whitish, mucous-like substance that looks like shredded tissue paper when floating in the water. The growth usually occurs when the sanitiser level has been inadequate or inconsistent. It is not harmful to humans, but is unsightly and can clog equipment. It also depletes sanitiser and oxidisers, which can allow other undesirable conditions to occur. Water mould usually begins growing in the lines, and by the time it becomes visible, the growth is often quite heavy.

To eliminate biofilm:

  1. Test pH and adjust to 7.4-7.6.
  2. Brush the entire pool, with special attention to areas around skimmer, inside skimmer and areas of observed growth.
  3. Add an initial dose of algicide to replenish depleted levels.
  4. Add 1 bag of Burn Out Extreme per 50,000 litres to the skimmer for light to moderate growth or 2 bags per 50,000 litres for heavy growth.
  5. Circulate for 24 hours and backwash the filter.
  6. Clean the filter with Filter Brite.
  7. Adjust feed rate for sanitiser to ensure maintenance of at least 2.0 ppm free available chlorine or 4.0 ppm bromine residual.
  8. A second treatment may be needed if any biofilm remains.