That's the bandwagon I'll jump on.
In 13 yrs now, with 10 systems on the go, I've never dosed trace elements or iodine in any form.
I raise xenia for resale through LFS
, and, I have lots of shrimp that have no molting problems.
I do test for and add calcium, alkalinity, and magnesium as required.
I saw a question on where do your trace elements come from and I want to say that my tank gets them from the salt mix, and, from the food that I feed the tank. All foods add trace elements to the tank, and many add iodine forms as well.
I do water changes, not to replenish trace elements, but to reduce the buildup of trace elements that comes from feeding the tanks.