Scientific research about swimbladder disorder for koi.  So for our very scientific minded koi lovers, this one is for you. 
 
Physostomous fish like cyprinids possess a swim bladder with a pneumatic duct in connection with the foregut, permitting the gas to enter into or be released through the alimentary canal. Due to this peculiar anatomic structure, bacteria and mycetes can potentially ascend the duct and colonize the swim-bladder. Besides inflammatory reactions, other swim bladder disorders include fluid accumulation, collapse, overinflation, and herniation. These swim bladder disorders and consequent buoyancy problems can be encountered in ornamental fish.
 
Animals | Free Full-Text | Swim Bladder Disorders in Koi Carp (Cyprinus carpio) | HTML (mdpi.com)