Sweet idea.(pun intended)
Unless you are gonna be gone for a full week or more there is really no need for feeders IMO. It is pretty hard to starve a fish to death.
A little off topic here but.... In college I had a 55gallon with jack dempseys in it, I left them alone for the entire winter break (about a month) with 60 or 70 feeder goldfish. When I came back they were no worse for the wear and only a few feeders were still swimming around. Point being... Your fish can take pretty good care of themselves, but the sweet potato idea is a good one if you have alot of herb/omnivores that you need to leave alone for a week or two.