Coral Essentials Reef Zeolite is naturally occurring, marine grade, zeolite rock, in a handy 2L bucket. Zeolite can absorb ammonia and other nitrogenous compounds and when used appropriately can quickly help reduce phosphate and nitrate in marine aquarium systems. It also has a micro-porous structure which makes it a very suitable environment for anaerobic bacteria. It is best used in a reactor, or can be used in filter bags in the sump as close as possible to the return outlet. Perfect for those looking to remove unwanted aquarium water elements and lower system nutrients in any marine aquarium or those wanting to maintain an ULNS (Ultra Low Nutrient System). Care must be taken not to remove the phosphate/nitrate too quickly and shock the corals. It is recommended to rinse the zeolite in freshwater before placing into a reactor or filter bag in your marine aquarium.