External filters are an excellent option for medium and large sized aquariums. Their large size and power means they are the most suitable option for larger aquariums, or those that are heavily stocked or house messy fish which produce a lot of waste. They are also a great option for those who wish to invest a bit more in a filtration system in order to cut back on aquarium maintenance. A larger filter means larger surface area for beneficial bacteria which means more waste can be broken down. Fluval New 307 External Filter The All-New 07 series marks the 7th incarnation in nearly 4 decades of Fluval's top selling canister filter family worldwide. Not only does the latest generation incorporate the power and reliability you’ve come to expect from the leader in aquatic filtration, but it also features several new performance upgrades that make it up to 25% quieter and more robust, energy-efficient, flexible and easier to use than ever before. Quiet Italian Precision-Crafted Pump Precise copper wound bobbin, impeller magnet, impeller fan blade, hardened alumina ceramic axle, rubber shaft mount and co-molded, high-flex polymer impel. Super compact external unit perfect for aquariums up to 330 litres!