Maintaining a Marine aquarium is a little more involved than a freshwater aquarium so the right equipment is imperative. This Service Kit makes it as simple as possible by supplying everything you need in one kit. The kit contains a replacement filter cartridge which is specifically for Marine biOrb (the biOrb Standard Service Kit should not be used in Marine biOrb as it contains a different mix of chemicals). A measured amount of high quality reef grade salt and water preparation chemicals are also supplied as well as easy to follow step by step instructions. The filter cartridge in your biOrb should be changed regularly. Frequency of filter changes depends on the size of your biOrb and the fish stocking level. On average it is recommended to change the filter every 6 to 8 weeks. Please refer to your biOrb instructions for further details. Kit Contains: 1 x Marine Replacement Filter Cartridge. 500g High Quality reef salt. 1 x Cleaning Pad. 1 x Water Treatment Sachet.