I have always been told that if a fish had swimbladder problem but was still able to feed then no need to euthanize - if it was so severe that the fish was unable to aim for food and therefore going to starve, I was told to euthanize.
Recently, I overheard my local aquarist telling someone that feeding fish a little vegetable matter sometimes helps with mild swimbladder problems - although I have no idea if this is true or not. Also, I have had fish in the past who had swimbladder for a short time then it somehow corrected itself (they were goldfish).
If yours is spiralling then that is probably the worst kind of swimbladder because when they have it that bad they can't usually reach the food, poor things. I had a beautiful 6" goldfish, Jess, who ended up with that type of swimbladder, spiralling like crazy. I was in tears watching him desperately trying to get to his food and missing it every time. I took him to my aquarist who put him to sleep for me.
Swimbladder can occur when a fish is added to a tank or at water changes, due to a sudden change of temperature. Also not enough roughage in their diet, apparently.
Regards - Athena