Okay, don't freak out if you recognize this topic from another message board...no opinions please, just the facts.
I was told by a dealer that both breeds (since 1968) and imports koi, that salt levels in Japan are always .6%. Folks at the other site dismiss the statement. I think it is important to consider as a koi hobbyist periodically introducing a new fish to a pond. Especially if the new koi has been kept with an imported fish.
I have sent a request to several importers in the US and one farm in Japan. I will request information from more Japanese farmers as I come across their email address.
If you have direct knowledge of salt levels (because you have been to the farms and have tested them yourself, you are an importer and have checked with your broker, or you are in direct contact with a Japan farm), please post your information.
I read an article within the last 2 months (I thought the author was Dr. Erik Johnson but cannot locate it in his library currently), that discussed what it was like to be a koi vet prior to the advent of Jpanese imports to the US. Diagnosing parasites and disease were typically routine. Since importing has increased, so have the difficulties at diagnosing and treating disease issues in US ponds. I can see this point of view.
Direct me to this article as well, if you have read it too.