Mineral substances needed by fish include calcium (Ca), phosphorus (P), sodium and chlorine (in the compound NaCI), manganese (Mn), iron (Fe), copper (Cu), iodine (I), and cobalt (Co). As with vitamins, minerals are needed by fish in a number that is not too large.
Calcium (Ca) and phosphorus (P) is required for bone formation / growth and to keep the body tissue function can work normally. Sodium chloride (NaCl) affected the growth, but its use is recommended not too much. Iron (Fe) is required for the formation of red blood cells, while copper (Cu) assist in the use of iron by the body. Iodine (I) is required for the production of thyroxine (a hormone timid) and manganese (Mn) influential in the process of ovulation / reproduction.
Source: Ir. M. Firdaus SAhwan, M.M. 2001.