Sponge filter is good for aquarium and provides both mechanical and biological filtration. The air infusion chamber produces numerous minute bubbles which promote gas exchange and increase dissolved oxygen level in tank water..Simply install an airline into the unit and provide both aeration and filtration for your fish..The sponge traps large waste particles mechanically and cleans the water without trapping baby fish..Product dimensions: 3.5” wide x 1.8” deep x 5.5” high; sponge dimensions: 1.8”D x 3.12”H. They are useful for as breeding filter or as secondary filter. Or they can be used as pre-filtration unit by fitting to an external or a top filter..Max tank size: Good for up to 15 gallon each filter. Package includes: 4 pcs of sponge filters in a poly bag.