If you are using RO water, it might be helpful, but if you are using tap-water I wouldnt worry about it. Im using Seachem's Reef Trace:
http://www.jlaquatics.com/phpstore/s...ID=sc-rtrc0500
It has iodide in it which is beneficial for softies and since im using RO water no trace elements are getting in to my water. I also use Reef Complete for Calcium/Strontium/Iodine. I rarely use my supplements, maybe only twice a month.
Chris