Mealworms are commonly used as feed for reptiles, fish, and birds. They grow best in well-ventilated containers eight to ten inches deep with large surface areas, and smooth sides to prevent them from escaping. The mealworms are mostly nocturnal and prefer a dark environment. The food for the larvae can be flour or cereals. Moisture is provided by small amounts of fruit or vegetable matter that should be replaced before it goes moldy.