Is it safe to turn my aquarium aeration off at night?
yes you can turn of the air pump at night. it depends really if you have gold fish i would say keep it on cause they like the air under the water cause when it is not they always go to the top. but i have a 200 litre tank and 10 tropical fish in it i have been looking after fish for about 5 years now and not that long ago i moved to tropical (cleaner and it doesnt need much maintenance). but yea if it is a cold water tank it would be best to keep it on. if it is tropical then yes you can turn it off at night just remeber to put it on now and again cause not all tropical fish need an air pump to thrive.