Housing "leftovers" is pretty easy. I have a glass tank (with a lid) that has a rodent water bottle, food bowl, and a hide. If you feed live, you're bound to have leftovers once in awhile. Having a simple setup ready will help you when this dose happen. Just make sure the rats have food and water at all times. Then, when feeding day rolls around again, offer the food then clean the tank. Pretty easy.