Duckweed is a true floating specimen that grows on the surface of the water in full sun to full shade. We sell 1/2 lb. well drained portions. A nutritious snack for larger fish as well as providing shade for smaller fish. Helps aid in algae elimination, as well as water purification. Duckweed grows faster in warmer weather. Add a pinch of miracle grow now and then to keep that lush green color and aeration to keep it growing! Grows quickly!