The Fluval U Series Media Value Packs are designed to deliver all the necessary media required to keep your filter at peak performance for up to 6 months. This pack was designed specifically for use with the Fluval U2 Underwater filter. Biomax's complex pore system offers maximum surface area to promote the growth of beneficial bacteria and maintain the nitrogen cycle. Simultaneously, Bio-Foam's structure helps maintain a consistent water flow, while still effectively trapping the majority of waste and debris. Finally, the Poly-Carb dual action cartridge traps fine debris and contaminants in the polyester layer, while the carbon layer filters out harmful toxins, discolourations and odours.