Mineral elements have a great diversity of uses within the animal body. The following mineral elements are recognized as essential for body functions in fish: calcium, phosphorus, sodium, molybdenum, chlorine, magnesium, iron, selenium, iodine, manganese, copper, cobalt and zinc. To these may be added fluorine and chromium which have also been shown to be essential for land animals.
The prominence of each mineral element in body tissues is closely related to its functional role. As constituents of bones and teeth, minerals provide strength and rigidity to skeletal structures. In their ionic states in body fluids they are indispensable for the maintenance of acid-base equilibrium and osmotic relationship with the aquatic environment, and for integration activities involving the nervous and endocrine systems. As components of blood pigments, enzymes and organic compounds in tissues and organs they are indispensable for essential metabolic processes involving gas exchange and energy transactions.