http://groups.msn.com/TheBettaObsession/illnessamptreatmentpart2.msnw
"Swim Bladder -Has a hard time swimming horizontally or cannot stay off the bottom of the container except when going up for air or feeding. A common problem in young bettas. It is not contagious and is due to overfeeding. Stop over feeding your betta/s (fry). They may return to normal, so do not kill them. Feed less and try a verity of foods. -Topbettas.com"
"TREATMENT: Bettas may recover on their own, but since overfeeding induces swimbladder disorders in most cases, the first thing to do is feed a lot less. Brine shrimp and too much of it is the biggest culprit, so if your bettas are bellysliding, stop the brine shrimp for a while and thereafter learn to have a more balanced diet, alternating brine shrimp with microworms or worms (depending on how old your bettas are). Do not kill a betta with a swimbladder disorder. It may recover on its own at any time, and is not suffering. Further more, the ailment is NOT contagious."
Did you catch the "Do not kill...the betta is not suffering" part? I know your fish was not a betta, but this goes for all fish.
I got all of this info in less than 5 minutes.
Alexa