Its presence is related to:

• The presence of humidity beneath the coating
• A lack of disinfectant beneath the coating
• Imbalanced water

Here is the treatment solution for eliminating this problem:

• Check the stabilising agent content level
• Lower the pH to 6.5: Use Acti pH minus powder
• Shock treatment: Acti HP granules 150g/10m3
• Scrub the traces
• Métalfix: 1kg/25m3
• Leave to act for 24 hours
• Balance the water in accordance with the recommendations of the Actisoft software (alkalinity, hardness, pH)