VETUS recommends having a spare fuel filter at all times. This can be done by changing over filters in a multi-filter system or by keeping a spare element on board.
A filter of 10 micron will filter out more dirt and will also become clogged sooner. A 30 micron element is recommended when the tank is very large, infrequently filled or the fuel used is of low quality. Filtration of 10 micron has text printed in blue and 30 micron has text printed in red.