Goldfish behaviors

Question
Our blackmoor gold fish has been swimming upside down  at times for a few months and is now floating upside down from the bottom to the top of the tank and stays there for several minutes at a time. He does not seem in any  distress, eats well, we clean the tank regularly and the other fish in the tank are healthy as well. There are 2 large goldfish, 2 blackmoors and an algae eater in a 75 gal tank. They were given to us 3 yrs ago so we think they are at least 7 or 8 yrs old. Our clients are teasing us that we are teaching this fish to "play dead" !! Thanks for answering our question..
Sandy

Answer
There is a condition where the swim bladder of the fish becomes damaged, pops, or is infected. Most of the time, this prevents the fish from swimming and they die. In this case, it just seems to be more comical than harmful. If you're really worried, try a few doses of a local antibiotic, espesially one that says it's effective against swim bladder infections. If he doesn't start swimming normally, but continues to be healthy otherwise, there isn't much else you can do for him and you should just let him be a happy (if a bit nutty-looking) goldfish.