I sincerely hope you didn't mean iodine, literally. :-) Iodide is chemically
nearly identical with chloride for most gross effects (thyroid special stuff
aside), so I can't see where 0.1 ppm is all that much as iodide.
Untergasser, for treatment, uses a stock solution of 0.5g iodine and 5g KI
in 100 ml of water. He then doses with 1 ml per 50 liters of tank water and
change water (1 drop per 5 liters).
-- Wright Huntley, Fremont CA, USA, 510 494-8679 huntley1 at home.com
In retrospect it becomes clear that hindsight is definitely overrated.