The biofilm or biolayer is a slimy layer on walls of water reservoirs such as silos, tanks, pools and so on. This biolayer consists mainly of slime producing bacteria and other organisms such as algae, viruses, fungi etc.
The biolayer is essential in the multiplication of these organisms.
Viruses, fungi and bacteria that are in the water need a biolayer to multiply. They use this biolayer as a kind of nursery.
This is a continuously repeating process, which means that in the long term high concentrations of micro-organisms are present in the water.
By keeping this biofilm away, it is impossible for microorganisms to multiply.