I don't think Koi and Goldfish viruses could be covered better than the following documents. These are things I found online visiting some sites while I got my USDA/accreditation. They open as flip books. You have to have Flash but they open plain, Flash, regular and mobile. Pretty neat.
The viruses covered include Spring viremia, the Herpes Viruses. Koi and Goldfish both get Herpes Viruses.
The BEST one of all is something you haven't seen unless you went for your Veterinary Accreditation for USDA and took the module – – Emerging Viruses of Koi and Goldfish.
Also a link or two to some recent videos I released lately.