Well, I'm not sure what you are asking if you have already decided what to dose. Once you choose a proprietary product, I'd probably stick with their directions.
In general. sodium or potassium iodide would be the easiest way to dose a known amount. Without knowing what Red Sea puts into that product, I can't really say how much to use.
With that said, I've not found iodide to be a useful additive, and that experience has been repeated by quite a few reefers over the years who used to dose it, then stopped and saw no difference. I dosed it for many years.