A variety of improved hydroclone based fluid filtering systems are described. The hydroclones generally include a tank having an internal chamber and a filter (preferably a surface filter) that is positioned within the internal chamber. The filter defines a filtered fluid chamber within the internal chamber of the tank. The hydroclone may be operated such that a vortex of flowing fluid is formed between the chamber wall and the filter with the filter being located in the center of the vortex. With this arrangement, the filter acts as a cross-flow filter. In one aspect of the invention, the filter is a stepped filter. In another aspect of the invention, the filter is an surface filter, as for example, an electroformed metal surface filter. In some preferred embodiments, the openings in the filter are arranged as slots that extend substantially vertically so that they are oriented substantially perpendicular to the flow path of fluid flowing in the adjacent portion of the vortex. In another aspect of the invention, a circulating cleaning assembly is provided in the hydroclone region. The cleaning assembly is arranged to help clean the filter and is driven by the vortex of flowing fluid formed in the hydroclone region of the internal chamber. In yet another aspect of the invention, improved hydroclone intake structures are described. The described hydroclones may be used to filter water and other fluids in a wide variety of applications.