Perhaps something from the goldfish. Or up the flow
Sent from my SGH-M919 using MonsterAquariaNetwork App
Sent from my SGH-M919 using MonsterAquariaNetwork App
Looks like spinal damage to me.
low oxygen have pretty much no effect on gar so high nitrates and the gold fish should be the problem. It does look like his back is not normal but it doesn't seem to be a too serious back injuries.Your temp seems a bit high. Higher temps=low oxygen. Low oxygen + high nitrates + goldfish is a recipe for disaster. I keep temps at 74-78 degrees and havn't had problems with oxygen. Good luck