Richard Smith said:I'm sure glad that our Pat doesn't charge THAT much for fish & chips!
$20,000 bucks a fish! That'd require at least a $500 pole and a $20 pedigreed worm. ;) :) :D
Anyhow, a dead koi is much like any other high-priced fertiliser -
a. Dead $1Million horse = $10 dog food.
b. Dead $20K koi = $5 plant food.
tac & ig & The Humbug Mountain Boys
Many years ago I had a black cat that roamed in the late evening and early morning. We are not sure where and how far away he went but he did bring home many, what I can only describe as quite large goldfish, leaving them on the lawn. He didn’t eat them and neither did the Herring gulls. 
We buried them. I guess he eventually depleted the pond where he got them from as the supply soon stopped.
Dan DeVoto said:Neat idea with Watercress... Never throught of that. We have had Koi in our large pond for over 30 yrs now and doing fine. We have one 3ft long, but most other are around 1 and 2 foot long out of about 70 of them. One of our kat tryed to get one at feeding time and got a little wet when was pull in the water.. hehehe..
Dan, I've had Koi for 12 years. They started out in the 4" range and now are over 20". Here in California over wintering is them sitting on the bottom from December to the end of January with no food. I've never fed them with any special diet to make it through the winter. As the Koi got larger they ate all my Water Lilies and other assorted plants. Now I plant Watercress in the nooks and cranes of the rocks, it grows like a weed. You can buy one bunch at Safeway and it will produce an unlimited supply, it roots in a day, the fish love it and it regenerates quickly. You'll need a good filter system they produce large size "waste". There's tons of info on the web. Good Luck.