2-Stage Filtration System The hygger Bio Sponge Filter provides mechanical and biological filtration to help keep water clear and your tank healthy. Fine sponge catches fish waste and tiny debris while bio balls provide plenty space areas for the colony of beneficial bacteia No More Fish Getted Suck up This small sponge filter is fish-safe seamless design without any moving parts, protecting small fish from getted suck up. Perfect for shrimp tank, quarantine tank or fry tank Aerate Water Not only can this fish tank filter keep tank water clean, but also it agitates water by making bubbles. It slowly moves water around which is great for fish loves slow-flowing such as betta and fry fish Air Pump Driven Filter Like most sponge filters, it requres an at least 2w air pump & an airline (both sold separately) to run with. Convenient plastic chamber allows for quick and easy access to filter media for maintenance or replacement Small For 2-5 Gallon Tank Size S measures 1.8 in W x 5.4 in H, suggest for 2-5 Gallons. Size L measures 3 in W x 7.3 in H, suggest for 6-20 Gallons.