A method of filtering a wellbore fluid can include receiving a wellbore fluid in a chamber. The chamber can be defined by an inner surface of a casing string that is positioned downhole in a wellbore. The method can further include filtering debris particles from the wellbore fluid by a filter assembly positioned within an inner region of the casing string. The filter assembly may include a plurality of slots and the filter assembly may be rotated by the wellbore fluid passing through the plurality of slots in the filter assembly.