Be very carefull if you have plants in your system. It doesn't take much salt to kill most plants unless they are salt tolerant. Iodine is not found naturally in fresh water bodies around the world, with the exception of a few of the rift lakes in Africa. No fresh water fish or crayfish requires iodine. It may not hurt, but it doesn't help. I've never used it.

If you have ich, heat alone won't kill it without killing the fish too. Heat will speed up the life cycle which allows the salt or other chemicals to act on the swimming portion of the life cycle. The level of salt needed for treatment is lethal to almost all plants you may want to grow. The fish should all be removed to a hospital tank to be treated. The ich in the aquaponic setup will die without a host in a few weeks. Be aware that many chemical treatments will make plants unfit to eat.

Here is a really good article on ich:
http://www.americanaquariumproducts.com ... m_Ich.html