Top tip:

It is advisable that you clean the filter medias in old aquarium water during maintenance. Do NOT clean the filter medias in tap water as chlorine and chloramines will remove the beneficial nitrifying bacteria that have colonised during the maturation of the aquarium.

EHEIM filter medias are some of the best in the world. They are highly efficient, developed in their own research laboratories, and made from the best raw materials. They are continually checked and are guaranteed to be free from any harmful substances.