Sponge filters work by aquarium water being drawn through the sponge from the displacement of water from the air bubbles. Debris is then trapped mechanically, and aerobic bacteria remove nitrogenous wastes. Sponge Filters are an ideal filter when raising fry as they cause no damage to fins and reduce stock loss compared to other forms of filtration. They are also ideal for hospital tanks.Rinse your sponge filter media as needed, usually once per week. Rinse your sponges in used aquarium water (preferred) or dechlorinated tap water using one of our dechlorinators, squeezing gently until the sponge filter media is clean.