No, you cannot use that to replace potassium. It would boost iodine way too high, and wouldn't be inexpensive to boost potassium that way.
FWIW, I 'm not convinced that anyone needs to supplement potassium, but for those who do, you might be able to get potassium chloride tablets from a pharmacist.
http://archive.reefcentral.com/forum...72#post8386972