Definitely remove the dead fish. Remove any decaying matter too.

On 14 Feb 2005 09:38:50 -0800, "Mike C"
wrote:

I took a peak under my pond cover and noticed 1 of my 6 Koi was dead.
It is laying at the bottom of the pond near where the other fish are.
Should I get it out or just leave it? I am a little concerned that
poking a net down there is going to really disturb the other Koi. Will
leaving the dead fish have a negative impact on the water quality (pond
is 500 gallons)? I am in Chicago and the water temp is around 40 now.