Sorry to step in, but Yes C5 did say to test. Mr X echoed that. Bottom line is the OP needs to test. If Iodine is low, then consider adding. If its not, then there is no need. It might be something else deficient, but I agree with X that if you are using a quality marine salt and doing regular water changes to re supplement everything, there is very little chance that anything will be deficient and very little chance that you will ever need to add anything.
C5...after you have been on this forum for a while, you will probably discover that Mr X is one of the more knowledgable folks on here (at least IMO
)...he's certainly not going off what other people have said for advice.