The B-BOX filter media fit into a cartridge modular setup system, which is versatile to use and easy to maintain. The modular cups are 100% reusable and interchangeable, allowing you to tailor your filtration setup to meet the unique needs of your aquarium inhabitants. Simply remove and replace the cartridges as needed for optimal performance. Due to the modular configuration of the B-Box filter system, it is possible to add a single extra modular cup to the Biobox filters, according to the needs of the aquarium water (attention: an extra filter cartridge may result in a decrease of the water flow rate).