Review on Penn Plax Smallworld Filter Cartridge by Stacie Stewart

Good for small bowl/tank. I would say no more than 2 liters. The bubbles can be quite strong and make the water hard for my betta. So I keep it low. So far the first filter changed after 2 weeks. At this frequency it can get expensive. The aerator that comes with the kit is good and fairly quiet. You don't need to buy another bubbler, as the "Customers often buy together" section suggests. (This bubbler is way louder, you won't like it.) I use the one that came with the kit.