I am with CN, don't dose what can't be accurately tested.
This would be another great canidate for my kids to work on if there were some way to determine the levels of each Iodine variant then the rest of the testing would be simple
to cloud the issue water sources and salt brands will not have the same levels between them.
IMO everyone here is correct in what they say but likely not completely extendable to another's tank. (adding or not adding)
It is hard to beat a simple water change for most problems in a tank. But like sps demand for calcium some softies and others may need more Iodine than water changes aload can keep up with.
If you do opt to dose, I would suggest going very slow and using only a fraction of what is on the bottle to start with and exercise great patiences in looking for results.
All I can say for sure is that my zoanthids are doing very nicely and I add nothing, not food, not iodine, zip o
is that my water, my salt, or a lower demand of the combined and confusing issues related to I in a captive tank I can not say.
again this is not a cut on what someone else does or suggests, their tank very well may need the supplimenting for one or more of the above reasons.
my two cents
Briney