can you put duckweed in an aquarium?

Greetings, fellow aquarists! If you’re anything like me, you’re always eager to explore new possibilities to enhance your aquarium’s beauty and benefit your aquatic companions. One such option that may have piqued your interest is duckweed, a small floating plant. But before you dive in, you might be wondering, can you put duckweed in an aquarium, and is it safe for your fishy friends? Let’s embark on a comprehensive journey to uncover the pros and cons of introducing duckweed to your aquatic world.

Key Takeaways:

  • Duckweed can be a valuable addition to your aquarium, but it requires careful management.
  • It serves as a natural water purifier and provides shade for your fish.
  • Duckweed grows rapidly, so controlling its growth is essential.

Let’s delve into the fascinating realm of duckweed together, and by the end, you’ll have a clear understanding of whether this unassuming plant is a blessing or a potential nuisance in your aquarium.

Duckweed in Aquarium: Benefit or Nuisance?

What’s in a Name

Before we explore the wonders of duckweed, let’s get acquainted with this miniature marvel. Duckweed is part of the Lemnaceae family, and the most common species you’ll encounter in aquariums is Lemna minor, often referred to as “common duckweed.”

The Natural Habitat

Duckweed is no stranger to freshwater environments. You can find it in ponds, lakes, slow-moving rivers, and, yes, even aquariums. This versatile plant thrives in calm, nutrient-rich waters, which is why it might hitch a ride into your tank, especially if you have live plants or fish that unwittingly introduce it.

A Closer Look: Identifying Duckweed

Spotting duckweed is a breeze. It boasts tiny, bright green leaves that delicately float on the water’s surface, resembling miniature lily pads. These leaves are usually about the size of a grain of rice. If you peer beneath, you might notice fine roots extending into the water, an intricate adaptation to anchor itself.

Is Duckweed Good for Your Aquarium?

The Upsides of Duckweed

  1. Natural Water Purifier: Duckweed is like a miniature eco-warrior for your aquarium. It’s incredibly efficient at absorbing excess nutrients, such as ammonia and nitrates, from the water. This translates to improved water quality and reduced chances of unsightly algae blooms.
  2. Shade for Your Fish: The floating nature of duckweed provides a dual benefit. It creates a serene, shaded oasis for your fish, mimicking their natural habitat and offering relief from harsh lighting.
  3. Fish Food on Demand: Duckweed isn’t just eye candy; it’s a tasty treat for many fish species. Goldfish, bettas, and more will happily nibble on these tiny leaves. This not only supplements their diet but also adds a touch of dynamic activity to your tank.
  4. Ease of Care: Duckweed is the laid-back plant of the aquarium world. It doesn’t demand specialized lighting, CO2 injection, or finicky care routines. It thrives in a range of water conditions, making it an excellent choice for beginners.

The Downside to Duckweed

  1. Unstoppable Growth: The same rapid growth that makes duckweed a water quality hero can also turn it into a formidable opponent. If left unchecked, duckweed can carpet the entire water surface, obstructing light penetration and potentially smothering other submerged plants.
  2. Competition for Nutrients: While duckweed absorbs excess nutrients, it can also compete with your other aquatic plants for those vital resources. If you have a lushly planted tank, the relentless march of duckweed might impede the growth of your prized specimens.
  3. Regular Maintenance: Managing duckweed requires regular attention. Without proper control, it can become an unwelcome takeover artist.

Is Duckweed Harmful to Fish?

Great news! Duckweed is generally not harmful to your finned friends; in fact, it can be quite beneficial. However, there are a few caveats to keep in mind.

Firstly, some larger or more aggressive fish may view duckweed as a delectable snack. If your tank features such fishy characters, maintaining a thriving duckweed population might prove challenging.

Secondly, while duckweed provides shade, an excessive layer on the water’s surface can reduce the light available to submerged plants. If you’ve cultivated a lush underwater garden, you’ll need to strike a balance between duckweed and your other aquatic flora.

How Fast Does Duckweed Grow in the Aquarium?

Prepare to be amazed by duckweed’s growth rate. Under favorable conditions, it’s like the Usain Bolt of the plant world, doubling its population in just a couple of days. This remarkable ability serves as both a blessing and a challenge.

On the bright side, duckweed’s rapid growth means it can swiftly absorb excess nutrients from the water, preventing the onset of pesky algae blooms and helping maintain pristine water quality.

On the flip side, if left unattended, duckweed can stage a coup and monopolize the water’s surface, leaving little room for your other aquatic residents.

How Do You Control Duckweed in the Aquarium?

The art of managing duckweed in your aquarium is a critical skill to prevent it from overwhelming your underwater kingdom. Here are some strategies to help you maintain control:

Manual Removal and Surface Agitation

For smaller tanks or when dealing with a moderate amount of duckweed, manual removal is the simplest and most effective method. Employ a fine net or your gentle hands to scoop out excess duckweed regularly. Combine this with gentle surface agitation from an air stone or filter outlet to keep the duckweed from forming an impenetrable mat.

Goldfish, Koi, and Other Duckweed-Loving Fish

If you’re struggling to keep duckweed in check, consider enlisting some underwater helpers. Fish like goldfish and koi are known duckweed enthusiasts. They’ll happily munch on the greenery and help control its population.

However, be cautious when introducing new fish to your ecosystem, as they should be compatible with your existing tank inhabitants. Additionally, remember that these fish require appropriate care and tank space, so make sure your setup can accommodate them.


Duckweed is a fascinating and potentially valuable addition to your aquarium. When managed thoughtfully, it can improve water quality, provide shade, and even serve as a supplementary food source. However, its rapid growth can turn it into a nuisance if left unchecked.

The decision to include duckweed in your aquarium should align with your specific tank setup and your willingness to monitor and control its growth. When balanced effectively, duckweed can be a delightful and functional component of your aquatic world.


Q1: Is duckweed harmful to my fish?

No, duckweed is generally not harmful to fish. In fact, it can provide shade and serve as a supplementary food source for many fish species.

Q2: How fast does duckweed grow in the aquarium?

Duckweed has a rapid growth rate and can double its population in just a couple of days under favorable conditions.

Q3: How do I control duckweed in my aquarium?

You can control duckweed through manual removal and surface agitation. Consider introducing fish that eat duckweed if it becomes a significant issue.

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