I'm left wondering, with so many hobbyists never adding anything but calcium and alk
suppliments, why would one want to spend money adding something that they don't even know what is in the bottle?
One of the most important rules of thumb in this hobby is: Never add anything to your tank unless testing shows there is a need for it.
Unfortunately, you can't test for what's in Marc Weis products as no one knows what to test for.
Personally, like many others, I do water changes primarily to REDUDCE the levels of trace elements which build up higher than normal salt water levels due to additions of food to the tank. Feeding the tank adds all elements in varying amounts, including iodine. Most of it has no way out of the tank without water changes.