If you have enough water circulation with your main filter (and you should choose a filter that gives you enough), the air pump is just for looks. So you should be Ok turning it off at night.
Now if the tank is overstocked, or the filter underpowered, etc. the airpump may be necessary to maintain enough aeration (esp. if your water temp is high). You might want to try shutting it off in the day time so you can watch your fish. <If they all gather at the top of the water gulping air ... you need more aeration!>
Another option is to put the airpump elsewhere .... some people put it inside a closet or even outside the room & run a long airline to the tank (you need a big enough pump to do that) .. or you can buy a quieter pump ....