This is a really strange story and Iīm making no claims as to its medical or scientific value. Iīm just telling it the way it happened.
In one of my tanks I have two goldfish, the smaller of them called "Hugo". About a year ago Hugo developed a swim bladder problem (which goldfish often do) that made him float like a piece of wood after eating certain kinds of food. Not too big a problem since he always seemed to get along anyway. About a month ago I suddenly noticed Hugo was missing from the tank. And thinking about it I realised I hadnīt seen him since the day before. No matter how close I looked I couldnīt find him and after taking the decorations out of the tank - still without finding him - I figured he must have somehow jumped out of the tank and been eaten by my dog (or something like that). And I finally pronounced him dead. Sad, of course, but he was several years old, and after all, fish donīt live forever.
Since the tank was stripped anyway I decided to do a water change and clean the interior filter. And as I pulled the filter out of the tank something fell from behind it. It was Hugo! He somehow must have wiggled his way into the small space behind the filter (normally less than half as wide as his body) and when he fell out he was folded double, with a severly torn tail fin and lots of subcutaneous bleeding making red streaks on his skin. He must have been trying to get out for quite some time and managed to mess himself up pretty bad.
He ended up on the bottom of the tank and barely moved. I felt very sorry for him and obviously my first inclination was to end his suffering. But then he slowly straightened out and tried to swim and I just couldnīt bring my self to do what had to be done. Instead I moved him to the 15 litre quarantine tank, put a little bit of antibiotics in the water and waited.
The next morning, amazingly, he was more or less back to his old self! Swimming around with his slightly bent tail, eating and showing no signs of wanting to be put to death. A few days later I returned him to the original tank and soon he was just fine again. The only remaining effect of his ordeal seems to be that - and this is where the story becomes really amazing - his swim bladder problem has totally disappeared! He now swims freely all the time - whatever food he eats.
I have no idea how this happened. Perhaps being compressed behind the filter somehow adjusted what ever was wrong with his internal organs. I most certainly donīt recommend folding your goldfish in half and stuffing them behind the filter to cure any swim bladder problems. But the fact remains, in some strange way, Hugo actually cured himself.