Don't use iodine. it's old school, and has too many potential side effects if you use it for too long.

Many people espoused iodine for years because prior to some of the more modern treatments iodine was the only thing that would kill cryptosporidium (which btw is pretty much not a problem in most places anyway).

Clorine dioxide based treatments such as Aquamira or pristine are as effective as iodine (they kill everything), work as fast or faster, and don't have a taste. They are as dangerous for side effects as municipal water treatement, since most of them are based on the same chemical process.

Short answer - go find aquamira (in canada it seems to be called "pristine") or an equivalend Chlorine Dioxide based treatement.