Flukes, also known as Trematodes are the most common almost ubiquitous parasite of Koi. And while Koi don’t die of primary fluke infestations, they DO succumb to the infections that Flukes carry on their hooks. The following are video and image media files that illustrate these parasites. The video links lead to videos I did which detail the treatments as well. (More on Flukes)
FLUKES and other PARASITES AND THEIR CONTROL