Koi in the winter

Question:

we just recently moved into a new home and inherited a beautiful 2500 gallon Koi pond with about 6 large fish and a few babies. we live in ohio so we have a deicer on the pond, we emptied out on the line of the waterful and pulled the pump out. We did add the beneficial bacteria. Is there anything else we should be doing for the winter? we know very little about the upkeep and i plan on taking a pond class in the early spring. A friend at work told me i should be putting non-iodized salt in the pond to protect their coats…should i? I just want to make sure my Koi live thru the winter. thank-you.