Reduce the iodine concentration of water?

Trying to raise tiger salamander larvae to become neotenic. I think the a low iodine concentration is the key. Right now, I think using a mixture of hose water and distilled water. With distilled making up the majority of the concentration. However their is more than just iodine in the water and I don't want to nutrient deprive them. Is their any way I can filter out iodine, without filtering other nutrients?