A new sponge can also be place right next to another sponge filter or in the substrate of the aquarium, which will seed it very quickly. This is excellent option if another sponge is needed quickly, for something like hospital tank.
Aquarium & Pond Sponge Filtration | How these Filters Work
The way a sponge filter works is very simple and need to be powered by an (buy separately). Air tubing is placed in the center of the sponge blowing the air from the air pump out which makes a pressure pulling water through the sponge. By this way, any floating debris in the water will be sucked into the sponge leaving your aquarium with the great looking water.
Aquarium Sponge Filter | ATI-AAP | Replacement Hydro Sponges
The missing of the sponge filter is chemical filtration that traps organic mater leaving your aquarium with the clear water. However, this type of filtration isn’t too necessary for a small fish tank with regular water changes and the truth is that people like to replace it with some more biological filtration.
Aquarium Sponge Filters - Angels Plus