Rootless Duckweed (Wolffia arrhiza)

Type:Floating Weed
Origin:Worldwide Spread
Growth Rate:Very Fast
Light Demand:Medium to High
CO2 Demand:Uses Atmospheric CO2
Care:Very Easy

Wolffia arrhiza (Rootless Duckweed) is a rootless aquatic plant belonging to the Araceae family. It is native to Africa, Asia, Australia, Europe, and parts of South America. It floats on quiet water bodies like ponds that do not have much flow. In the wild, the duckweed of Lemna and Spirodela genera often grow along with Wolffia arrhiza.

The plant can grow only up to 1 mm and has a roundish body. It is the smallest vascular plant on earth and produces a flower that has a single stamen and pistil. Wolffia arrhiza grows primarily through vegetative propagation. In the aquarium, it is more useful as an alternative food source than for aquascaping. Almost all aquatic creatures including fishes, frogs, crustaceans, flukes, and dragonfly larvae eat this plant.


Other names for Wolffia arrhiza are Spotless watermeal and Khai-Nam. This plant has a high nutritional value both for humans and animals. It contains proteins, amino acids, minerals, vitamin B12, and trace elements like calcium, magnesium, and zinc. Wolffia Arrhiza also serves as a food source for humans and is especially preferred in Burma, Laos, and Thailand due to its inexpensiveness, fast growth rate, and high nutritional value.

It is also used to absorb nitrogen and phosphorous from the wastewater from black tiger shrimp farms and other industries. The plants grown in such wastewater are widely using to feed different animals like chicken and fish.

Water Conditions

Wolffia arrhiza grows in neutral to alkaline waters. The growth rate is very high when the water is more alkaline and the temperature above 21°C. When water conditions or temperature are not ideal, it sinks forming a turion. This turion contains about 40% of starch. When the conditions become ideal again, it becomes active and floats on the water, and quickly propagates.


It is very difficult to maintain Wolffia arrhiza in the aquarium since its size makes it an ideal snack for practically all aquatic creatures. It is easier to maintain a separate culture and harvest it regularly. The plant grows very fast and can double its number within 3-4 days. It simply needs sunlight, nitrogen, and phosphate-rich water to grow.

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