The man decided to build for one of his goldfish suffering from a specific disease "wheelchair"that helps the pet swim in the right orientation. Vets give sick fish a few weeks, up to months, but the Korean fish has been alive for 5 months since getting sick, and it looks like he is doing well. See for yourself how this bizarre invention works.
Fish bladder disease occurs when the organ becomes dysfunctional due to intestinal parasites or constipation. In most cases, it can be cured by feeding the fish with peas or by having the veterinarian have a procedure of inserting a small stone into the swim bladder. I know it's quite cruel reasoning, but most aquarists do not want to incur expenses several times higher than the cost of buying a fish.
The average life expectancy of a goldfish is between 10 and even 15 years.