A resin media, which is used to remove ammonia and other harmful substances. Zeolite is an excellent filtration media for small tanks and as an emergency media to remove sudden rises in pollutants. Although very effective at removing ammonia, zeolite quickly reaches its maximum holding capacity. At this point zeolite can be 'recharged' by soaking in a salt solution overnight. Once recharged zeolite can be returned to the aquarium filter where it will continue removing chemicals and pollutants.