The Hydro Filter utilizes reticulated filter foam for higher flow rates. It provides both mechanical and biological filtration. Aerobic bacteria colonize the sponge, providing a bacterial substrate to facilitate the nitrogen cycle. In addition, the Hydro traps larger waste particles mechanically cleaning the water. Maintains the biological filtration when the main filter is changed or cleaned. Prevents debris such as dead fish and plant material from clogging the intake by distributing the suction evenly down the length of the sponge. Prevents small or baby fish from being suctioned into the main filter or water pump. Traps larger waste particles, mechanically cleaning the water. Includes a variety of adapters for use with various water pump intakes. Can be used in the vertical or horizontal position. Easy to clean. Just rinse and squeeze. Fits most water pumps and filters. The Pro series of sponges have a larger weave, or less dense material than the standard style. Info from Aquarium Technology, Inc.