Fluval FX Gravel Cleaner Kit. The FX Gravel Vac quickly connects to all Fluval FX4 and FX6 (2nd generation) canister filters for the ultimate convenience in powered substrate cleaning. Effectively traps dirt and debris Integrated filter housing with Fine and Super Fine vacuum bags (Item # A372 and A373 – sold separately) Thumb-operated flow control Gravel guard prevents clogging Vacuum head with grooved design for efficient debris collection Tube extension included for larger tanks and hard to reach areas Easily stores within FX lid-mounted clips For use in freshwater and saltwater aquariums.