The wet/dry external filter generation is full of innovative technology for aquarium sizes up to 600 I. The wet/dry technology of this external canister filter series fills and empties the filter material and the useful purification bacteria come into contact with a high level of oxygen. The purification bacteria work more intensively, thus effectuating extremely efficient decomposition of pollutants. We call it a 'breathing" change-over contact which is regulated by a reliably functioning wet/dry floater compartment. After filtering only cleaned water with a high oxygen content returns into the aquarium.