Lemna minor (aka Common Duckweed, Lesser Duckweed, or simply Duckweed) is a notorious plant among the fishkeeping community. This plant is such an efficient grower, it is often considered a nuisance! It is a very common floating plant that is also very small. In fact it is one of the world’s smallest flowering plants. It has a distinctive appearance, small with two or three leaves. Each leaf produces one short, spindly root.
Care Level: Easy
Preferred Water: pH 6.5 to 8, No hardness preference
Minimum Lighting: Moderate to Bright
Temperature Range: 42.8°F to 91.4°F (6°C to 33°C)
Leaf Size: Length, up to 0.04″ to 0.3″ (1 mm to 8 mm)
Duckweed is found all over the world. It can be found on all continents, except for Antarctica; however, it is not native to Australia or South America. If you investigate a slow moving body of water, such as a pond or lake, chances are you will be able to find this plant at the water surface. It can also be found in swamps and roadside drainage. Since it is a floating plant with short roots, it tends to collect at the point in a body of water that the flow is heading towards. In a lake or pond, this could be a drain or around the entrance to an outflowing stream. In a body of water with a lot of dissolved nutrients and bright sunlight, the entire water surface can be covered by a layer of Duckweed.
Duckweed reproduces primarily through division. The parent plant simply sprouts a daughter plant and the process continues, as long as there is light, water, and nutrients. It produces tiny flowers, but division is the much faster and preferred method of reproduction. Duckweed has a phenomenal growth rate, and it can quickly cover the entire surface of a still body of water.
Interestingly, in temperate climates Duckweed can overwinter by storing starches when temperatures begin to drop. The plants then sink to the bottom of the body of water and await for spring, when temperatures begin to climb again.
In the Aquarium
Oh boy, people have opinions on Duckweed in the aquarium. Personally, I find it simultaneously beautiful and nightmarish. Once you have added Duckweed to your aquarium, it can be incredibly difficult to remove it completely. If only a single leaf is left behind and allowed to reproduce, the entire colony can be regrown in a few weeks or even days. Having said that, if you are keeping fish that eat Duckweed, like goldfish, this can be a free and easy supplemental pet food.
Duckweed has high nutritional value, which makes it an ideal pet food. I recently wrote a guide for turning Duckweed and other surplus plant material into homemade fish food.
Because of its incredibly fast growth rate, Duckweed is also a valuable ally in the battle for better water quality. Those spindly little roots soak up a tremendous amount of nutrients from the water column, which helps to clean it as well as inhibit the growth of algae. The downside to this is that it can also negatively impact your other aquatic plants. If Duckweed is allowed to grow at its desired volume and rate, you will likely need to supplement nutrients for your other plants. You must also regularly thin the mat of Duckweed at the water surface to allow adequate gas exchange and penetration of light.
Duckweed as Food and Fuel
As mentioned earlier, Duckweed is surprisingly rich in energy and nutritional value. This has inspired some to call it a “superfood.” It is incredibly high in protein (20% to 40%) and low in fiber (<5%). This makes it a valuable and readily digestible food for livestock and aquarium pets alike.
Due to its low cellulose content (about 10%) much of the energy of the plant goes into producing starches. The amounts are comparable to other terrestrial biofuel crops, but unlike those, Duckweed does not require expensive pretreatments. Source: Wikipedia.org
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Featured image source: Wikipedia.org