Definitely better to keep the same size pipe. The flow would be a little stronger at the point it enters but the reality is that the pumps in canister filters are no where near powerful enough to create a lot of 'pressure' in the lily pipe. What would really happen is you would just cut your flow down which you probably do not want to do.filter 850l/hr, my hose diameter is 16/22, aquarium 60cm. Will choosing a smaller lily pipe, 12mm one, create a stronger outflow current due to the smaller size and pressure or is it better to just pick a 16mm pipe?