These 4-sided, microfiltration pad cartridges are made with high-quality resins that help remove harmful ammonia, nitrite, nitrate, colours, odours and more to help improve the quality of the water in your aquarium. Quickly and easily improve the water quality in your aquarium with the help of these API Nitra-Zorb SZ4 Filter Cartridges. Part of a multistage filtration system, these cartridges help remove toxic ammonia, nitrite, nitrate, colours, odours, heavy metals and toxic gases with a 4-sided design. The water passes through the high-quality resins in the cartridge for chemical filtration that reverses cloudy and degraded water quality issues. The no-mess, easy-to-change design allows for simple use. Filter cartridges for mechanical filtration Cleans and clears aquarium water by removing toxic ammonia, nitrite and nitrate Multistage filtration system removes colours, odours, heavy metals and toxic gases, which cloud water and degrade water quality, for goodhabitat conditions (filter not included) 4-sided pad cartridge is filled with high-quality resins for chemical filtration All of the water passes through the cartridge for excellent efficacy without bypass No-mess, easy-to-change filter cartridge for simple use Available in a 2-pack and 4-pack *See menu selections above for sizes and styles in stock and available online.