Hydro-Sponge filter provides both mechanical and biological filtration. Aerobic bacteria colonize the sponge providing a bacterial substance to facilitate the nitrogen cycle. In addition, the Hydro-Sponge traps larger waste particles mechanically cleaning the water without trapping the baby fish. Information Capable of moving more water than other sponge filters. One inch diameter lift tube allows use of power head* without adapters. Raised off bottom, no dead space. Heavier base. Can be used with or without an airstone.* Easy to clean. Just rise and squeeze under cold running water.