Duckweed is lighter green, grass green in color These tiny green leaves float on top of the water. It is an excellent natural food for pond fish. Each plant is smaller than the eraser on a number 2 pencil. Duckweed is the smallest plant in the plant species world!
NOTE: most do not grow duckweed in the pond but grow it outside of the pond in large containers to grow to feed it to their fish. If you have a skimmer this plants will very likely end up in the skimmer unless you have fish that eat it quickly. My own guys get 3 pounds a few times a week.
It is hardy zone 5 or higher