Do you have powerheads providing strong current in your tank? My Florida Gar does this too and he's 11 inches in a 450 gallon tank but I have 10000 gph of current going on in there.
Oh sorry I just read through the whole thread. Sorry for your loss. I would assume its the current from the powerheads disrupting your gars swimming pattern. There's no way it would kill it. Mine is perfectly fine and eating lots even with the massive strong currents in my tank. Must be some other odd cause of death. Again sorry for your loss.
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