You need to make sure that the pets in your household have their food no matter what. Lets put it this way, you can starve but the animals can't they cannot go to the store. So try and get some fish food
I feed my goldfish an unpeeled, unskinned orange once a week. I stick it in there for half an hour (no more than that, and you should keep an eye on it), and then take it and any pieces out. This also helps prevent constipation from a high protein diet. So it is safe to feed them other things, but only as a remedy. They won't die from different foods, and it makes them happy to have a little variety. I've also heard cooked and deskinned peas are good, as are bananas and cooked lettuce. Just remember to take any excess out after 30 minutes, other wise they might over feed, it will cloud up the water, or could even clog the filter.