Sera siporax is a highly effective long term filter medium also intended for smaller bio filters one liter of siporax has the same capacity as 34 liters of ceramic or clay filters and therefore is the best value for your money on the market all other filter media are much more expensive based on the surface area of one liter of siporax in the siporax bio film organic matter decomposing bacteria grow rather than nitrifying or denitrifying bacteria this means that the pores of the filter