Methods for producing clean liquid/wax products from a slurry used in a Fischer-Tropsch reactor are disclosed. In general, one embodiment of the present invention comprises a solid/liquid filtration system having a filter medium comprising a substrate and a filter cake deposited on the substrate, wherein the filter cake is generated by deposition of solids from the slurry. The thickness of the filter cake can be maintained within a desired range by controlling the slurry velocity and/or the pressure differential across the filter medium. This invention relates to a method of operation of such filtration system which increases filtration cycle time and improved filtrate quality resulting in very low solid content in filtrate.