Specifically, trace elements are barium, chrome, cobalt, iron, copper, manganese, nickel strontium, zinc, bromine, flourine, iodine, lithium, molybdenum, selenium and vanadium to name a few.
Trace elements are part of the essential yet sometimes overlooked natural makeup of sea water. Not only is sea water comprised of salt (which gives it that salty taste) and carbonate, calcium and magnesium (known as the major elements). It also includes minute or trace amounts of multitude of the elements listed above and more.
Think of trace elements as the fish equivalent of human supplements. These supplements boost health and well being of your inhabitants, as well as colour and vibrancy especially noticeable in relation to SPS coral.