It is theoretically possible just to do water changes in a lightly stocked tank and have the parameters stay good enough without measuring them. This method is what many fish stores use as they are always adding make up water when the send a bag out of the store.
The rest of us have to measure parameters, Mg, Alk & Ca to keep them rocking steady over time to be successful with delicate corals, especially hard corals & all the pretty sticks. Fluctuations in parameters is hard on corals and will make keeping them long term difficult if not impossible.
If you are going to do water changes, get an API Calcium test (crazy cheap but good enough) and get your alk and Ca stabilized. I like natural sea water levels, but if you are using salt with elevated levels that can work too, just find a way to keep them steady.