I have heard some people say that it is necessary to cover dishes at night time.

Answer

Utensils containing food should be covered. This is necessary according to the Hadith. Shaitaan does not interfere with covered utensils. If the dish is left open, shaitaan will interfere with the utensil and the food. Empty utensils should be inverted and not left open. It is also mentioned in the Hadith that during the course of the year there is a night in which an abundance of calamities descend. These calamities will settle in open dishes.