The Fluval U Foam Filter Media is available for a number of the Fluval Filters, and should be changed periodically as the foams start to deteriorate, ideally every 3 - 6 months or so. There is other media within the larger filters which will also need changing too, such as the Poly/Carbon Cartridge, and Bio-Max.
The Foam Pads have been designed to remove fine waste from your aquarium via mechanical filtration, and aid in the colonisation of good bacteria. Each pack contains two sponges, with the exception of the U1 foam block that contains only one.
These foam sponges capture particles within the tank, such as fish waste and uneaten food, and ensure they are removed from the water, keeping it looking clearer. However they do require regular cleaning in order to stay effective, otherwise they will start to block up. Each sponge set is custom cut for the filter for a perfect and effective fit. These can be used in freshwater or marine systems.