big koi, about 9 years old.
No idea what happened , it seemed fine up until today .

What I would like to ask of you all is if you had ONE good broad spectrum multi-purpose med. to keep on had for going the ( slap my hand) shotgun approach what would it be ?
This fish had no obvious signs of anything wrong with it , am at a loss.
Everyone else in the tank other than the " crooked one" appear fine also, hope they STAY that way !

I put some tetra pond fish treatment in the tank along with some koi vital hoping to prevent anymore fatalities , keeping my fingers crossed.