i feel you're pain, i lost a koi earlier this year which was dropsy i was heartbroken, i have 8 other fish in with her and they were fine but i did seperate her for a week before she passed, she seemed like she was getting better then the following day she had died :(
i hope you can maybe save yours but dont worry it wont pass onto you're other one
hi sean its pennywort i bought 1000grammes on ebay, ?10.
i use mesh net because of local cats and herons, i dont want to lose stock.
children eating koi lol hmmmm thats odd!.
i am a angler and wanted my pond as natural as i could get it, i didnt want crystal clear water and i added plants that you tend to find when fishing, also the pennywort is simular to lily pads but smaller but do grow.