Fluval U1 Foam Pad The Fluval U Foam Pads captures large particles and debris for effective mechanical filtration, the crucial first stage in the filtration process. It is custom-made to fit perfectly inside the filter chamber to prevent debris bypass. The Foam Pad has a pore size that allows efficient water flow, less clogging and long-lasting filtration. The Fluval U Foams are suitable for freshwater, marine or reptile environments. Genuine Fluval filter media Captures large particles and debris for effective mechanical filtration Custom-made to fit perfectly inside the filter chamber to prevent debris bypass Pore size that allows efficient water flow, less clogging and long-lasting filtration Designed to fit the Fluval U1 Filter (A465)