Why is my fish isolating itself?
Your Koi could have a parasite or a bacterial infection. You may want to catch the Koi with a net and inspect it for any external problems.
Minnesota Koi keepers may contact Dr. Amy Kizer at Lexington Pet Clinic if they have a Koi with a health problem.
If you live elsewhere and require assistance, get in touch with a veterinarian that specializes in Koi health in your area or an AKCA certified Koi Health Advisor.