I have been using an Eheim autofeeder for about a year non-stop. That is the only way I feed (plus fresh greens for rabbitfish). The fish get 3 generous feedings/day. I replenish the food in the feeder about 1/month. Once in a while some water gets splashed into it by one of the fish, and the food gets all stuck together, but that is the only problem I have had. I don't know if the food changes in quality over time though - it looks the same and never grows mold.