Hydro-Sponge: -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. -Easy to clean, just rinse and squeeze under cool running water. The Hydro-Sponge Filter provides both mechanical and biological filtration. Aerobic bacteria colonize the sponge providing a bacterial substrate to facilitate the nitrogen cycle. In addition, the Hydro-Sponge traps waste particles mechanically cleaning the water without trapping the baby fish.The Pro series of sponges have a larger weave, or less dense material than the standard style.