I was using a trimmer near my pond and accidently chopped into some nettle
plants, pieces of which flew into the water. Then, two days later, the
biggest goldfish (6"+) got sick -- it looked like it was trying to cough
something up, then it just lay over and stopped trying and after another day
passed it died and I removed it from the pond. None of the other fish
(there are about forty) seemed to be affected. Does anyone have any
experience with goldfish eating nettle plants? I thought maybe the big fish
ate a piece of nettle leaf and got poisoned from it, but my wife is
doubtful.

I know the leaves retain their nastiness after soaking in the water, because
I cleaned the pond over the weekend and got a big-time nettle sting from a
plant part that was on the bottom. My hand was still burning twelve hours
later.

David