Poor Dick.
One of my friends has a tank full of fancy goldfish. One of them had a smiliar problem, but he wasn't as advanced in years as this fellow.
His, though, appeared to be brought on by overeating. He was a bit of a pig, especially when it was live worm night, and would eat himself into oblivion, then spend the next hour or two swimming upside down near the top of the tank until he was able to fishfart his way back to being upright.
(It took them a while to recognize when he had finally joined the fishafterlife, since they were used to him looking dead. Apparently REAL fish don't have eyes that look like little "x's" when they croak.
)