I assume you are talking about a mechanical one. You should be able to set how much food it puts out, although I have read other users saying it overfeeds, but then cranking it down a notch might be better. I don't think anything measures proper amounts of food like a real person unfortunately, so I wouldn't rely on one all the time for daily feedings if you are able to feed the fish yourself. If you're on vacation for a weekend, I would just skip feeding just for the weekend.