It is important for the quality of the surface finish that the plating solutions are kept free from particulate and build-up of organics does not occur.
Most finishers will have a recirculating loop on the plating bath that includes a particle removal filter such as a bag, depth or surface (pleated) cartridge. Intermittently, a carbon cartridge is used to clear up the organics that build up from environmental conditions and elements directly introduced, such as the components and racks.