The amount of iodine in table salt is non-toxic to koi and GF. Be careful of anit-caking agents. Salt to 0.1% can ease stress and will still allow the use of most meds. Roark's homepage has great info on water chemistry and some handy calculators. click2roark.com Register with a legit e-mail address for access to his homepage.
5" with or without fins? Either way it is a very young fish, and may not have been up to the stress of handling and transport. What is/was the water temperature?
Please tell me you quarantined the new purchase...... I consider failure to QT abhorrent.
