Key Features Effectively Keeps Aquarium Clear, Clean and Healthy Easy to Fit Sucker Mounted Support Four Stage Filtration Easy Clean. Slot in Filter Cartridges. For Coldwater or Tropical Aquariums. For Aquariums of up to 12 -35 Lites (2.6 - 8 Gallons). Service Packs available The Interpet Internal Cartridge Filter is the ultimate in compact filters for your Aquarium. Using an effective four stage filtration, the filter pumps the dirty water through the four layers to produce clear and healthy water. Stage One . The water passes through bio media which acts as a home for essential bacteria which removes toxic fish waste. Stage Two . Mechanical floss then clears the water by trapping fine waste Stage Three . The water then passes through carbon which purifies the water by removing dyes, toxins, heave metals and odours. Stage Four . The final stage has a unique Algaway pad that reduces unsightly algae by removing phosphate, algaes favorite food. The result is crystal clear and healthy