The filter cartridge in your biOrb should be changed every 4-8 weeks. This pack includes everything you need for 3 filter changes. A new cartridge is supplied in the Service Kit as well as a special cleaning pad for removing dirt and algae from the inside surface of the biOrb and water preparation chemicals for carrying out a partial water change. The kit also contains easy to follow step by step instructions. Includes Water Optimiser to help keep your biOrb's water crystal clear. 3 x Offical Reef One Filter cartridge, 1 x Aquarium Cleaning Pad, 1 x Water Conditioning treatment.