I have a tenant living downstairs complaining that she can hear the
filter at night and it's bothering her. She sleeps directly below the
tank, and there is indeed a slight hummming. Would I be able to switch
off the filter at night from 10.30pm to 6.30am, or would this be a
major no no?

I have a 72 gallon freshwater tank, with a gravel and sand substrate
(no underground filter) and an AquaClear 110 filter.

Jon