There is a popular saying in the reef hobby "Don't dose anything you're not testing for". I think this is really important. Adding too much of anything will have a detrimental effect on what you keep. With that said, it also depends on the corals you intend on housing. As an example, if you are keeping SPS
, calcium levels are crucial and a reactor would be in order......or at the very least Kalkwasser additions to replace evaporation. But here again, it is important that you are testing for Ca
so as to gauge where you need to be (450) and where you currently are at on a daily basis.
Magnesium and Iodine are important for soft corals. Strontium is not as critical as some think. Also take into account the size of your tank. If it is a smaller reef of under 65 gallons, small water changes every other week (even as little as 5%) are helpful in replacing trace elements so as to avoid dosing.
As a side, carbon strips trace elements and aggressive protein skimming can as well. The best indicator of anything is whether or not the corals are thriving.
Nothing wrong with wanting to join the camp of hobbyists that do as little as one water change per year. I have seen a lot of successful reef tanks where water changes are not employed.
The conventional wisdom is to dose calcium in a reactor, GFO
in another reactor to strip phosphate, and skim with a small fuge in the sump to house live rock rubble, sand or mud, and macroalgae under a lamp. This set up seems to work well and requires very little by way of water changes.