Josh gave you the best advice, "If you don't test for it, don't add it." After your tank cycles testing is pretty much a no-brainer... Nitrates-fixed by water changes and cutting back on those feeding frenzies, Calcium and Alkalinity-gotta add something sometimes, Magnesium - maybe, but most salt mixes handle that, Strontium and Molybdenum - dang, Kent made some buckeroos on that stuff, Iodine - its mainly for cuts if you lived in the 50's, I have vintage bottle FULL and a test kit covered with dust - water changes seems to be enough (Lugol's makes up into a great "tick dip" for ailing corals, tho).

I use carbon from time to time to get the yellow out, but even so, I have no compelling urge to pee in the sump... well maybe that one time after all those margarita snails..no salt please, I have plenty!