The Fluval U1 internal filter is suitable for aquariums up to 45 L. The U series underwater filters have a three stage filtration which is ideal for use in fresh, marine or reptile environments. Stage 1 foam removes large particles, Stage 2 poly/carbon cartridge traps fine debris, improves water clarity and removes impurities and then Stage 3 BIOMAX provides optimal biological filtration efficiency. The Fluval U series range are ideal as supplemental or stand-alone filters, silent, efficient, simple to install and easy to maintain. Filter media included is 1 x Foam. Flow rate 250 litres per hour.