Whole organisms can provide vital food elements missing from commercially prepared pet foods. The internal organs, bones, and other components of the prey of your pets may be nutritionally complete foods for certain species. Also, many interesting salt and freshwater aquarium animals will accept live food only, and it is often impossible to switch these species to substitute diets. In this chapter, you will learn about the natural histories of a number of species used as food for aquarium pets, and learn how they are obtained and raised in captivity.