Why Culturing The Outside of the Koi is Poor Diagnostically

Bacterial cultures taken from the outside of the fish, or directly from the ulcer can be badly misleading because you’re collecting germs from the fish and the water column.

When you biopsy the fishes’ surface, you biopsy the fish pond. What’s ON the fish is a mix-n-match of every bacteria in the pond is NO commentary on what is actually IN the fish, killing it.

The following video discusses this concept and I hope, describes the important idea of culturing the kidney in a sacrificial fish, or culturing blood taken from the caudal peduncle.


Dr Erik Johnson is a Marietta, Georgia Veterinarian with a practice in small animal medicine. He graduated from University of Georgia with his Doctorate in 1991. Dr Johnson is the author of several texts on Koi and Pond Fish Health and Disease as well as numerous articles on dog and cat health topics.