We added all kind of things to our tank in the food. Many trace element are toxic at higher dose and water change will remove these trace toxin. The problem with a close system is some substance get use up while other get more concentrate and become toxic. If we know what get use up, we add ( like Ca and carbonate), but we cannot export many thing by mean other than water change.
I have done them all, from not changing water to short term 100% weekly water change and all in between. My tanks do best when I change water regularly.