The PP Biochambers are specially tailored for both drum filters. They are very easy to assemble with flexible couplings. The biochambers are equipped with rubber membrane aerator(s) and PVC connection 20/25mm for the air pump. The grids in the biokamers have a gap opening of 8mm (therefore not suitable for KNS and pond chips/flakes). The ideal filter medium is Helix/Helix Plus. BK60: max. 150 liters of media, BK90: max. 350 liters of media.