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Duckweeds offer one of the most ideal habitats for aquatic life. The lush green cover they provide makes an aquarium appear as natural-looking as possible, which mimics your aquatic specie’s wild habitats. And as you may know, this ambience of nature is vital for any thriving aquarium. Not only that.

Duckweeds are also effective absorbers of phosphates, nitrates, and toxins in your tank. They go all out to improve your water quality by preventing the accumulation of toxic chemicals.

Even so, duckweeds can be lethal to your animals if not grown strategically. Which is why it’s vital to know every important thing there is to Duckweeds before introducing them to your tank.

Check out this short but comprehensive guide:

Origin of Duckweed

Also known as bay root or water lens, duckweed is a tiny floating plant that’s found in virtually all types of aquatic environments. Initially documented in the 20th Century, native populations of Duckweed grow in Southeast Asia, Australia, Africa, and North America. Duckweeds seem to not grow in the Antarctica areas only.

Even so, their growth prevalence in a particular area depends on the Duckweed specie. Note that Duckweed falls under Lemnoideae – a subfamily of flowering marine plants. And under the Duckweed family, there are two major genus- Lemna and Wolffia.

If anything, those belonging to genus Lemna are prevalent mostly in America and Southeast Asia while those under Wollfia thrive in Africa, Australia and parts of America too. But the main reason why Duckweeds grow in numerous places is that their grains get transported across by water current, wind, and birds.

Duckweed Appearance

In wild areas such as ponds, sloughs, and lakes, Duckweed appears like an extensive mat on the surface of water bodies. If you’re not careful, you can easily mistake them for algae. However, Duckweeds feature a simple structure with a somewhat modified stem.

Every individual plant (genus Lemna) has one oval flat-leaf, that’s no more than ¼ inch long fused with the stem. The duckweed inflorescence, consisting of one tiny pistillate flower (in a poach-like sac) and two microscopic staminate flowers is almost invisible. And despite their diminutive size, Duckweed flowers still attract bees, flies, mites, and small spiders.

Taxonomists believe that the duckweed flower is a modified version of the familiar club-like spadix and leafy spathe of calla lilies, Jack-in-the-pulpit, skunk cabbages, and most members of the Araceae (Arum) family.

Duckweed Water & Light Conditions

Duckweeds are quite easy to care for and will grow in any kind of aquarium, though they truly thrive and proliferate wherever water has little current. And because of their impressive growth rate in still waters, you’re likely to experience explosive growth rather than subdued. Still, the following conditions should suffice for Duckweed to flourish fast:

  • Water Temperature Range – 68 to 86 °F (20-30 ℃). Temperatures outside this range will inhibit Duckweed growth and make the plants dormant.
  • pH – 5 to 7.5. But they can still survive in any pH under 9.
  • Light – Duckweeds are photosynthetic plants, which means they require enough exposure to sunlight every day for photosynthesis to take place. If you can’t place your tank where there’s enough sunlight, consider installing high-quality full-spectrum fluorescent light.
  • Nutrients – Duckweeds can’t grow heavily without an adequate supply of NPK (Nitrogen, Phosphorous, and Potassium). It’s advisable to add trace minerals as you perform weekly water changes.
  • Water Current – Your tank water should be completely tranquil, especially at the surface.
  • Salt Content – As low as possible. A presence of salt content will inhibit the growth of your duckweeds.

Duckweed Maintenance

It’s important to note that Duckweeds can double their numbers in just 3 days! As such, you have to control this overgrowth to prevent its harmful effects. If you don’t go out of your way to maintain Duckweed growth, expect your tank’s oxygen to deplete, its filter to clog and its appearance to look unsightly.

With that in mind, you can control the Duckweeds in your aquarium in the following ways:

– Mechanical Control

It’s one of the easiest control methods and involves removing duckweeds consistently by scooping using either your hands, a net, a rake, etc. This method is most effective when done repeatedly.

– Biological Control

This method involves keeping herbivore aquatic animals to consume the duckweeds. Some ideal examples include koi fish, carp, and tilapia fish.

Nevertheless, biological control is most-effective when duckweeds haven’t become so densely populated that plant-eating fish can’t keep up with their growth rate.

– Using an Aeration Device

As mentioned earlier, duckweeds thrive in still or very slow-moving waters. You use this fact to your advantage by introducing an aeration device in your tank.

This device creates turbulence, which goes a long way to inhibit duckweed growth. The only downside is that this method is relatively expensive compared to those aforementioned.

– Use of Chemicals

Without a doubt, this should be your last result. When all else has failed, you can introduce herbicides like fluridone and diquate bromide to kill duckweeds. However, be careful not to contaminate your tank water. So strictly adhere to the package instructions.

Another effective method of controlling duckweeds is limiting the sunlight your plants receive. And don’t rush to implant in-house duckweeds if you can’t do the following:

  • Disinfect your duckweed, especially if it’s from a suspect source. Using a weak solution of potassium permanganate or bleach can help get rid of the snails and parasites that sometimes come with these plants.
  • Monitor your duckweed growth daily. And scoop out any plants that surpass the half mark (surface area) of your water tank.
  • Move your filter 4 inches below the water surface to protect it from clogging. Also, wrap it with a cheesecloth to act as a primary filter.

Duckweed Propagation

You can grow duckweed indoors by following these simple steps:

  • Buy about 50- 100 duckweed pods and place them in a container.
  • Disinfect the duckweed.
  • Place disinfected duckweed in a tray (plastic) with 12-14 inches of depth. Add fresh water or tap water to the tray. Not salty water.
  • Position the tray where it can receive 10 hours of sunlight daily. Or use fluorescent bulbs to provide ample lighting for the plants
  • Perform weekly changes of the water in your duckweed tray.
  • After about ten days, the duckweed will multiply and you can use a net to transfer the plants to your fish tank.

An Excellent Addition to Any Aquarium

Despite its disadvantages, Duckweed offers benefits no aquarists should ignore. It’s a constant source of food for fish and helps to maintain an extra cool environment in your tank. So consider adding Duckweeds in your tank today. You won’t regret it.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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