A biofilm is created when an abundance of bacteria starts to adhere to solid surfaces, such as the walls of your spa. The bacteria find food in organic contamination such as skin flakes, hair, oil, ... The bacteria will multiply rapidly and will surround themselves with a layer of sludge. even small channels are created in that mucus layer that provide nutrients to all bacteria. Before you know it, this biofilm will be a big problem. That is why the use of Aqua Pur 5 in 1 is essential. This product detaches the biofilm from the walls and sends the dirt to the filter.