Duckweed (Lemna Minor) plants are perfect for fish tanks and ponds as well. Turtles love to eat them, frogs swim and hide in them, baby fish hide in them, and they provide a filtration source as well. Duckweed helps to filter the water by soaking up ammonia and nitrates very effectively which helps keep the water nice and clean.

Not only do they look beautiful, they reproduce easily, can act as a natural shade for fish/critters below the surface, and help clean the water. Floating plants do best with less water flow, so you want to keep the water somewhat still that they are being put into.