Most freshwater fish have adapted to not eating everyday and can go up to 3 months without eating, but after getting used to the dailyfeedings, I doubt they would enjoy not eating for a month, but a week should be fine if there is very little food in the substrate (very little so it doesn't cause an amonia spike) for them to sift out, and there is algae for them to graze, but even if either one of these didn't fall in to place, they would still live through it and only end up hungry in the end(until you feed them).