In principle, filtering should as be fine as necessary, not as fine as possible. In general the filtration grade is defined by the manufacturer of the related device. These days this information is sometimes stated with figures in μm for the theoretically largest particle just allowed to pass (e.g. 10 μm or 25 μm).
However, as a 10 μm filter allows a specific number of 50 and 100 μm particles to pass, the filtration grade should be characterised using the β value (beta value).