Although it's November my pond (700 gal) weed is still growing and now
covers the surface. The fish snooze below. I've switched off the pump, but
I'm a bit concerned that not enough surface is clear to allow sufficient
oxygen to dissolve. Should I clear some of the weed? I'm not too worried
about freezing as I live on Vancouver Island, close to the sea, and it
doesn't get very cold . I hope I'm not tempting fate.

You might be.

The water hyacinths in my pond were let go, and they finally covered
the whole surface of my pond.

ALL my fish died.