Nardoo (Marsilea Angustifolia) with floating ring

Common Name  - Nardoo
Latin Name  - (Marsilea Angustifolia)
Perennial
Position  -  Full sun to part shade
Flowers  -  No         
Submersible - Yes to a depth of 30cm
Foliage - Produces foliage that floats on the surface of the water
Origin - Native to Australia
Cover - Great surface cover for fish
Oxygenator  -  No
Size  -  30cm diameter

Interesting to know,  the seed-like spore cases of Nardoo known as sporocarps can be eaten as a porridge or dough.