Check the listing for details. sera PrefiX Filter Passive Add-On Pre-Filter Quick-Filter or Media Reactor. Condition: New. Listed at 49.99 USD. sera PrefiX Filter Pre-filter, bio filter, quick filter or media reactor for connecting to pumps or external filters.The sera PrefiX Filter allows enhancing the filter volume of a connected filter by up to 1.6 liters (0.4 US gal.) with two variably useable filter baskets. The motorless filter is, for instance suitable as a prefilter in case of cloudiness, as a quick filter in case of pollution or as a biofilter for expanding the filter capacity of small external filters. The filter can be connected to a pump or an external filter by means of a sera hose 16/22 mm. Connecting several PrefiX filter in series is also possible. In case of fine grained filter media, using the sera filter media bags 1 or 2 is recommended.