Healthy fish can easily go a week without food.
If you are only going away for a few days, don't bother getting someone to feed your fish. Fish feeders are available which dissolve slowly and release food but these may upset the ph in your tank. If you're going away for longer than a week you will have to make arrangements for someone to feed the fish. You will probably have to find a friend or neighbour willing to call by every few days. The fish don't have to be fed every day, and shouldn't be given more than one days food at a time, even if they've gone a few days without.