Sera’s PrefiX Filter can be used in case the volume of a filter is not entirely sufficient. It includes two filter baskets that can be variably used and equipped, and enhances the filter volume by up to 1.6 liters (0.4 gal.). The motorless filter can be connected to a pump or an external filter by means of a hose (diameter 16/22 mm). It is also possible to connect several PrefiX Filters in a series and thus increase the filter volume. The filter provides various applications: as a prefilter in case of cloudiness, as a quick filter in case of strong pollution or as a biofilter for enhancing the filter capacity of small external filters.