^ What he said. Your salt mix already contains it, and one little shrimp is not going to deplete that. If you keep doing water changes, you automatically replenish it (and boron, selenium, and a laundry list of other useful elements.) Don't ever let anybody sell you an additive without selling you a test specifically for it, so you can be sure you're not overdosing: the short version is---don't dose what you don't own a test for. Just as you can overdose yourself on vitamin/mineral pills, all the way to toxicity [they become poisonous]---you can overdose a tank on supplements.
I agree with all of the above. If you are not overloading your system with inverts and do frequent water changes you shouldnt have to dose for it. And if you have tons of inverts, I would still recommend getting a Red Sea iodine tester first and checking your levels. Red Sea test kits in my opinion are the most accurate and would recommend them for testing for everything.