I have heard many opinions, but in my own, I believe gar are quite tough. I am still skeptic as to what the cause of death really is...As in Jordan's story, there was no telling how long that gar was out of water flopping around. It was missing most of its slim coat and was drug around by the snout by a cat...If this isnt tough and stressful on a fish, I dont know what is...As soon as this fish was put back into the tank, it slowly floated to the bottom to rest, and in about a day was close to being right back to himself with no visible problems.
How long was this gar in your tank before it actually died? was it acting weird right from the minute you put him in there, or did he seem alright, and them get progressively worse?
With the lose of its use of the back fins, can a broken back truly be ruled out as a possible cause of death? An injury such as this, mixed with the stress of being moved and placed into a different tank could all be the resulting death.