I have about 25 hermits, and I have an array of shell sizes that are vacant for use. Probably 40 loose shells around the tank, but these are the first two I have found dead, I know my midas is extremely protective of his cave, and that is where I found them both dead. That was why I was questions, I have seen him smack them around before when they come to close. So you believe there may not be enough iodine?