The most important liquid parameters affecting media selection are temperature range, pH and the presence of solvents. Most skimmer manufacturers offer polymer media, some also offer stainless steel. Cost is a consideration as any medium has to be replaced from time to time. In tube and mop skimmers, the user is restricted to polymer because of the medium's shape. Belt skimmers can use both media types, and depending on design, may allow easy switching if one proves unsuitable.
Some designs allow a change of media type without changing pulleys.
Others require different pulleys for different media, making modifications more difficult. Polymers are good for applications where abrasive particles are present, or when physical abuse can occur. Some tube shaped polymer media are coated with an oleophilic material to improve oil adhesion, which may diminish over time as the coating is scraped off by the wiper blades or debris. In mop configurations, polymer fibers may get matted down fairly quickly by higher viscosity oils, reducing removal capacity. Some polymer media are laminated to improve resistance to stretching.