Maximum optimization of biological filtration The original sera siporax Professional is suitable for use in both freshwater and marine aquariums as well as in ponds. Not depending on the kind of filter (internal/external/trickle filter), it maximizes the surface required for biological purification and provides the optimal substrate for the settling of necessary filter bacteria. sera siporax Professional 15 mm siporax Prof 10L 2,9kg D/US/F/NL/I/..