Yeah, your shrimp will grow another arm, unless it dies of iodine overdose

really there's just no reason to add heavy metals to your tank; okay, maybe iodine has some use to marine animals, but do you have a test kit? Like a lab-quality way of measuring trace metals? I sure don't , and I've never added any metals to my tank, but I'm certain if I sent a sample to a lab, I'd come up higher than NSW levels in all metals. They're in salt, municipal water, food, dead animals, etc...