[pdabbadabba]

Well, this assumes that the local populace will reliably eat the spirulina. The nice thing about salt, is that you only have to solve the problem of getting people to eat the salt that you've iodized. You don't have to solve the additional problem of getting them to eat salt in the first place.

If you're running some sort of anti-malnutrition campaign that involves local cultivation of spiritual then sure, why not add iodine to it? (Assuming that this is technically feasible. Don't know whether it is or not.) But if you are trying to solve the specific problem of iodine deficiency, then I'm not sure why you would start with "first, grow a bunch of spirulina..."