Dying Floating Pond Weed
 

Hi, I have a small (100 gallon} pond with a few Koi. During the summer good
shade cover was obtained from water lilies and aggressive water hyacinths
which was allowed to cover 2/3rd's of the pond. Now that the weather has
turned cold the plants are dying and leaves are going black. Should I
remove these dying plants or leave them to cover the fish through the winter
months when it could ice over?? Will the decay jeopardize the water
quality? Can anyone tell me the consequences or make recommendations.
Thanks Tony