Sponge filters provide both mechanical and biological filtration - Traps floating debris and protect your baby fish from being sucked up into the filter, aerobic bacteria colonize the sponge providing a bacterial substance to facilitate the nitrogen cycle.
 
Simply install an airline into the unit and turn on the air pump, great way to clean and oxygenate your tanks; Easy to clean: simply squeeze the sponges in tank water. Two sponges means more surface area for beneficial bacterial colonization and faster cycling, keep your fish tank crystal clear and clean.