Plant Profiles: Duckweed


Plant Profiles: Duckweed

So, you’ve got your fish swimming with vibrant colors, and your decor perfectly capturing the underwater ambiance.

But something’s missing, right?

Now it’s high time you add the final touch with beneficial aquatic plants.

A top contender? Duckweed.

This tiny floating aquatic species from the genus Lemna is not just one of the smallest flowering plants but a powerhouse in sustaining aquatic health.

Despite being among the smallest flowering species, duckweed’s role is anything but minuscule.

As a floating plant, it paints ponds and water bodies with a lush green tapestry. Yet, for all its wonders, duckweed often remains overlooked, overshadowed by its more flamboyant aquatic counterparts.

It’s time we brought this aquatic wildlife into the spotlight, don’t you think?


Overview and Facts: Duckweed Plants

Duckweeds, part of the family Lemnaceae and subfamily Lemnoideae, are free-floating aquatic plants. They commonly grace still waters or those that are slowly moving in large amounts.

By now you might have an idea that these little green plants are actually the smallest flowering plants on Earth.

And get this, they’re called “duckweed”. Why?

Well, it’s a fun tidbit! These plants are a favorite snack for ducks.

As they float on a pond or other calm waters, ducks often graze on them as they swim by and even transport them to other bodies of water sometimes!

So, the name duckweed kind of paints a picture of where they’re commonly found and who loves to eat them!

5 Genera of the Lemnaceae Family

Dive deeper into the world of duckweed and you’ll find diversity. The Lemnaceae family houses five genera, and across these genera, there are 38 unique species, each having its role in nature.

  1. Landoltia: A relative newcomer to the duckweed family, distinguished mainly by its slightly elongated fronds.


  1. Spirodela: Often referred to as “giant duckweed”, it’s larger than other genera but is still relatively small. It has multiple roots per frond, giving it a distinct appearance.


  1. Lemna: Perhaps the most commonly recognized, the genus Lemna has a simple, flattened body and a single root per frond. It’s the genus where you’d find the familiar Lemna minor.


  1. Wolffia: The smallest of the duckweeds, they have no roots and float entirely on the water’s surface. It’s notable for having the smallest flower in the plant kingdom and it’s not myth! It is actually a fact recognized by the Library of Congress.


  1. Wolffiella: These have a more elongated shape compared to the more round Wolffia. Rootless like its cousin, it drifts gracefully in quiet water.

Origin and Habitat

If you’ve ever taken a stroll near a calm pond in North America, the still backwaters of streams in Europe, or the swamps of Asia and Africa, chances are you’ve come across duckweed plants.

They are often mistaken for algae and are closely related to the water fern, which means they grow in similar aquatic habitats.

Most duckweeds, like the widely recognized Lemna minor from the genus Lemna, prefer the surface of shallow and stagnant waters. Think of places like ponds, lakes, ditches, and swamps.

But it’s not just stagnant waters that have their heart; one species, the star duckweed (Lemna trisulca), grows on the cooler, flowing waters of spring branches and streams.

Duckweed growth is not limited to wild water bodies, though.

Native to a vast expanse that includes North America, Central America, Asia, Africa, and Europe, duckweed displays remarkable resilience.

In North America alone, they’ve been known to withstand the cold winters, thriving even in USDA plant zones 4 through 10.

Duckweed Growth Rate

Ever noticed how some plants just seem to have a knack for bouncing back, no matter the odds? That’s duckweed for you.

And when I say no matter the odds, I mean season changes, water temperature drops, and even those unpredictable nutrient fluctuations. These little aquatic plants thrive in diverse conditions!

You know, it’s almost like they have a built-in survival instinct.

In ideal conditions – think lighting, and a good dose of nutrients like nitrogen and phosphorus – duckweed doesn’t just grow; it explodes!

They can double in population in mere days. It’s like watching a nature-based time-lapse in real time.

Now, while this rapid growth can be a boon for our fish, birds, or other species that fancy a duckweed snack, it can be overwhelming in a smaller pond or a home aquarium.

So, if you’re thinking about introducing duckweed to your aquatic space, just remember: keep an eye on them. Duckweed grows too quickly when the conditions are right!

Appearance and Size

If you’ve never seen duckweed plants before, it’s easy to mistake them for a random green scum on the water’s surface. But lean in closer, and you’ll see they’re anything but random.

The common types in the genu Lemna like the Lemna minor and Lemna minuta? They’ve got these small, simple, flat bodies that almost look like miniature green coins. Their circular or oval fronds are typically less than 1/6 to 1/8 inch across, with 1-3 clusters. Each leaf then possesses a root that hangs down the water.

But if you want something more robust, try Spirodela polyrhiza, often called the “giant duckweed.” It’s larger and has 2-20 roots hanging down per frond. The size of each frond in this variety can approach ⅜ inch across, making them easily distinguishable.

And then there’s Wolffia globosa. Oh, my word, it’s the tiniest of them all but it sure stands out!

They have no roots nor stems, and again, have the world’s smallest flower.

Benefits of Having Duckweed

While they offer a food source for ducks and other waterfowl, duckweeds also work hard at cleaning up. They help oxygenate water, absorb excess nutrients, and even provide shade for other aquatic life. They even reduce the presence of harmful algae in the water.

But here’s where it gets exciting: many species of this aquatic plant are known for phytoremediation.

It might sound very science, but in simpler terms, duckweed plants are just natural water purifiers, capable of treating waters contaminated with metals.

Recent studies on duckweed genomes have shed light on their unique abilities to purify water and adapt to various environments. This is also why the removal of contaminants using duckweed systems has shown promising results in wastewater treatment research.

Simply put, it’s really good at filtering and making water cleaner.

Their quick growth and ability to reduce microbial and phytoplankton presence make them invaluable for a pond and research alike.

So, those tiny green specks on your pond? They’re doing a lot more than just floating around!

Caring for Duckweed: Tips and Tricks

Thinking of bringing some duckweeds into your waterscape? Let’s set the stage for them!

At their heart, these tiny green wonders thrive in waters with rich nutrient availability, especially nitrogen and phosphorus. This is one reason they can often be found in waters impacted by agricultural runoff.

They have a penchant for stillness, preferring the calm waters over turbulent currents. And sunlight? They just can’t get enough of it.

But where’s the thrill without a little bit of challenge, right?

These plants are quick to reproduce and can cover a water’s surface before you know it. It’s a beautiful sight, sure, but unchecked growth can tip the balance of your waterscape. So, while they’re low maintenance, a bit of attention and understanding can ensure that your duckweed stays a charming accent rather than becoming an overwhelming blanket.

Water Parameters

Water Parameters

While duckweed isn’t excessively demanding, paying attention to water parameters will ensure it grows healthily and benefits your entire tank ecosystem.

  • pH Level: Aim for a pH between 6.0 and 7.5.
  • Hardness: Soft to moderately hard water is ideal. A range between 5 and 15 dGH (degrees of general hardness) works best.
  • Nutrient Levels: As previously mentioned, duckweed has a soft spot for nutrient-rich environments, especially when it comes to nitrogen and phosphorus.
  • Temperature: Aim for a range between 68°F and 82°F (20°C to 28°C). Sudden fluctuations can stress the plant, so try to keep it stable.
  • Ammonia, Nitrite, and Nitrate: Duckweed can tolerate these compounds to an extent and can even help reduce them. However, it’s essential to maintain levels safe for all tank inhabitants. Keep ammonia and nitrite levels as close to zero as possible and monitor nitrate levels, ensuring they remain below 30 ppm.

Remember, regular testing and adjustments will keep your green carpet in prime condition!

Water Movement

Water Movement

Duckweed has a preference for the calm and quiet, naturally gravitating towards peaceful waters.

If you’re introducing them into a tank or aquarium, be mindful of strong currents. Filters and water pumps should be adjusted so they don’t push or damage the duckweed.

And while surface skimmers are great for removing debris, they might remove duckweed too, so keep an eye on them.

In larger bodies of water, like ponds, consider natural barriers like rocks or plants. These can help maintain pockets of stillness, ensuring your duckweed thrives. Remember, for duckweed, tranquility is key.



Duckweed thrives best under optimal lighting.

For duckweed in a pond, full sun exposure is ideal. However, these adaptable plants can handle varying light conditions. If you’re cultivating duckweed in an aquarium, find a spot that gets a minimum of 6 hours of sunlight daily.

The right lighting ensures they form dense colonies on water surfaces. This rapid growth, however, can lead to potential issues like oxygen depletion in a pond if not monitored. In turn, fish kills can occur due to reduced oxygen levels.

So while these plants are known to float and cover the water surface of ponds and lakes swiftly, they should be managed effectively.

Fertilizer and Carbon Dioxide

Fertilizer and Carbon Dioxide

Fertilizing can provide a boost, but it’s crucial to do so in moderation. Nutrients, especially nitrogen and phosphorus, can accelerate their growth.

Start by selecting a liquid aquatic plant fertilizer tailored for floating plants, ensuring the nutrients are easily absorbed. It’s crucial to follow the manufacturer’s guidelines, but if in doubt, diluting the fertilizer is a safer bet.

Rapid expansion might signal that you’re over-fertilizing, risking the suffocation of other aquatic species and potential oxygen depletion.

Consider the natural nutrient intake of your pond too; if it’s already getting nutrients, especially from sources like agricultural runoff, you might need to adjust or even skip added fertilization.

Just like fertilizer, additional CO2 usually isn’t required in natural settings like ponds. They absorb it from water and the atmosphere.

In aquariums with fish, the animals’ respiration provides enough CO2 for duckweed. However, in plant-dense tanks without many animals, consider CO2 supplementation. Use a diffuser or an injection system, start with minimal amounts, and adjust based on the plant’s response.

If duckweed thrives, your conditions are likely balanced; if not, reassess factors like lighting and nutrients.

Planting Duckweeds


Duckweeds are one of the easiest to propagate. They naturally reproduce via budding, where small “daughter” fronds emerge from the parent plant.

Within a few days, these daughters become independent species. If you want to introduce duckweeds into a new water body or aquarium, simply take a scoop from an established source and spread it onto the water’s surface.

Is Duckweed Plant Invasive?

The term “invasive” can be subjective, but in the context of duckweeds, they can certainly become dominant in the right conditions.

Their rapid growth rate, especially in nutrient-rich waters, can lead them to cover entire water surfaces if left unchecked. While they provide benefits like water purification, they can also block sunlight penetration, affecting other aquatic life beneath.

Therefore, while they might not be invasive in the traditional sense, imbalances in the ecosystem can occur due to their overpopulation.

How to Prevent Overpopulation

Duckweeds, with their rapid growth, can quickly cover the entire surface of a pond if left unchecked.

While this might be a desirable trait for some applications, such as wastewater treatment, in a decorative pond or small water feature, it can affect the growth of other aquatic plants and reduce oxygen levels, harming aquatic wildlife.

To prevent duckweed from overpopulating:

  1. Regular Skimming: For manual removal of excess duckweed every few days or as needed, you may use a fine net or a skimmer.
  2. Introduce Natural Predators: Certain fish species, like goldfish, grass carp, and koi, will eat duckweeds. Introducing them to your pond can help control its population.
  3. Maintain Nutrient Balance: Duckweed thrives in nutrient-rich waters. Ensure that you aren’t over-fertilizing your pond, and if possible, introduce aquatic plants that compete with duckweed for nutrients. Moreover, you may opt for water additives that contain bacteria and enzymes that compete with the nutrients vital to duckweed’s growth.
  4. Limit Sun Exposure: Duckweeds grow faster with abundant sunlight. If overpopulation becomes a concern, consider adding shades or aquatic plants with large leaves to partially block sunlight, slowing duckweed’s growth rate.
  5. Aeration: Using a fountain or bubbler can disrupt the calm waters duckweeds prefer, reducing its spread.
  6. Regular Monitoring: Keep an eye on their population and act quickly if you notice a rapid increase in their numbers. Early intervention is the key to effective management.

Aquascaping with the Smallest Flowering Plants

Aquascaping with the Smallest Flowering Plants

Duckweed’s petite and simplistic beauty offers an effortlessly elegant top layer. Aside from that, duckweeds are like the unsung heroes of the water gardens.

Easy to grow? Check. Low maintenance? Absolutely. And the best bit is, whether you’re an aquascaping newbie or a seasoned pro, duckweed’s got your back!

You can find it in almost any aquatic store, making it a breeze to add to your setup. So, if you’re looking to give your space that extra touch of natural charm, why not give this plant a shot?

Now, if you are looking to create a multi-layered visual treat, pair them with some taller and submerged companions! Water fern, java moss, anubias, cryptocorynes, and hornwort are going to be your best friends.

Together, they create a symphony of textures and heights, making your space sing with natural beauty.

Tankmates for Duckweed

Tankmates for Duckweed

Smaller, less aggressive fish like tetras, guppies, and mollies are great choices, as they tend to coexist harmoniously without decimating the duckweed population.

Shrimp, especially cherry shrimp, make perfect companions, contributing to both the aesthetic and functional balance of the tank.

Snails, with the mystery snail and nerite snail being prime examples, seamlessly fit into this environment.

Additionally, introducing frogs and newts can offer an engaging dynamic. While they might not interact with duckweed directly, their presence certainly enhances the overall biodiversity and energy of the aquatic habitat.


  1. Can I use duckweed as human food or fish food?Absolutely! Duckweeds have a significant nutritional value and have been explored in environmental science studies as a potential food source for humans. Additionally, waterfowl like ducks often feed on them, and fish like koi and grass carp in many ponds find them appetizing.
  2. Do any scientific studies delve deeply into duckweeds?Indeed. There have been biosystematic investigations and even a monographic study dedicated to understanding duckweed, its growth patterns, and its place in the broader family of Lemnaceae.
  3. Can duckweed help control harmful bacteria in my pond?Duckweeds can contribute to maintaining water quality by absorbing excess nutrients like nitrogen and phosphorus, which could otherwise promote the growth of harmful bacteria and algae. However, duckweeds alone may not completely control harmful bacteria, so it’s essential to maintain a balanced ecosystem and monitor water parameters regularly.
  4. Are all duckweed species suitable for my aquarium?While many duckweed species can thrive in aquariums, it’s essential to research the specific requirements and growth habits of the species you plan to introduce. Some may grow rapidly and cover the entire water surface, potentially shading other aquatic plants, while others may be better suited for controlled aquascaping.
  5. Can I grow multiple species on the water’s surface in my pond?Yes, you can cultivate various species simultaneously on the water’s surface in your pond, creating a diverse and visually appealing ecosystem.
  6. Are duckweeds suitable for an outdoor pond in colder climates?Yes, many species of duckweed are hardy and can survive in a wide range of temperatures. They are often used in an outdoor pond, even in colder regions, as long as the water doesn’t freeze completely.
  7. Can duckweed and algae be used for phytoremediation in polluted waters?Yes, both duckweeds and certain types of algae are used in phytoremediation processes to purify contaminated waters by absorbing pollutants.


In conclusion, duckweed may be small, but its significance in the world of aquarium plants cannot be overlooked. Their rapid growth, nutrient-absorbing capabilities, and role in phytoremediation make them a valuable addition to any water garden or aquarium.

As you embark on your journey, remember that the world of water gardening and aquariums is a vast and rewarding one.

If you’re seeking further guidance or wish to connect with fellow enthusiasts, consider joining our Facebook community. With over 470k aquarium enthusiasts, you’ll find invaluable insights, shared experiences, and a warm welcome awaiting you!


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