Very informative.this will help,
There is no valid reason to use only non-iodized salt yet this is always a hot topic for discussion and argument among aquarium hobbyists. In reality, the minuscule amount of iodide that would end up in a treated pond or aquarium is likely to be beneficial (as a potential source of essential iodine for both certain plants and animals) and certainly not harmful.Salt and Its Uses
The Use of salt (sodium chloride, NaCl) in the freshwater aquarium or pond. What is salt? In the broadest sense a salt is the chemical compound formed when an acid reacts with a base. There are many salts in our everyday lives: baking soda, or sodium bicarbonate, NaHCO3, and washing soda...www.monsterfishkeepers.com
Thank you