You feed fish during the day when the light is on. If you feed them 3 times a day and the light is on for a 12 hour period, that’s once every 4 hours 3 times followed by 12 hours of rest. What analog timer can do that?
That’s not going to work if you’re going on a vacation for a week. You want to fill the feeder with a week’s worth of food at a time and have it feed every day according to the schedule. Control the power to the feeder with a smart plug and set the feeder’s internal timer to 4 hours.