Regular water changes, for the most part, will replace your trace elements. Other than that, what you need to watch is maintaining your ph, alkalinity, calcium levels.
Adding such things as iodine, magnesium, and other minerals individually can lead to alot of trouble. Theres no way of accurately measuring iodine. Its also poisonous if you overdose, which is easy to do. Basic rule of thumb, if you don't test it, don't adjust it.