Bubble Magus Media and BioPellet Reactor is an internal multi-purpose fluidize media reactor that can be use with carbon, GFO, or Biopellets. With a small spacing saving design with an energy efficient pump that draw water from below and creating an up flow water movement toward the top of the reactor and exit out the top. Maintenance are a breeze, by loosing the 4 thumb screws at the base or on the lid. 3 way to use this reactor: Carbon reactor: Leave sponge and bottom plate as pictured. GFO reactor: Remove bottom sponge only. BioPellet reactor: Remove bottom plate, bottom sponge, and top sponge.