Let's not give up on the zoas. I get it. 2 drops (total) for 60 gallons will not crash the tank. With that said; suggest sending your water to one of those test centers or get the red sea pro iodine kit. It will provide a reading. Ball park. Be sure and follow the temperature soak for the reference sample. I added some iodine per the local fish store owner. Not the bottle. And the zoas came to life.What happens if you over do it? Will it crash the tank?worst case scenario? I dont know if it is worth adding at all for just zoas I have others I am much more attached to. I