I had someone feed my 2 tanks once when I left for over a month. They didn't think anything was in the 1 so it never got the light turned on or fed.
The Common Pleco, Catfish, and Jaguar Cichlid were all still alive when I arrived home, obviously very hungry but they made it despite my fish sitters negligence. They lived for years after as well with no ill effects.
-Not suggesting anyone not feed for a month, just sharing is all.