Duckweed (Lemna minor) is one of the smallest flowering plants in the world and one of the fastest-growing floating aquarium plants available. Native to freshwater environments across the globe, Duckweed forms a dense green carpet on the water's surface, providing shade, reducing algae, and absorbing nutrients at impressive rates. Each plant consists of just one to three tiny oval leaves with a short root dangling beneath. While its rapid growth is one of its greatest strengths, it also requires careful management to prevent it from completely covering the aquarium surface. Duckweed is highly valued in shrimp tanks, fry rearing setups, and aquariums where excess nutrients need to be controlled. Compliance note: Duckweed is restricted or regulated in several U.S. states; always check your local regulations before purchasing.
Common Name: Common Duckweed, Lesser Duckweed
Scientific Name: Lemna minor
Origin: Worldwide (freshwater environments)
Placement: Floating
Maximum Height: 0.1–0.2 inches (leaves), roots up to 0.5 inches
Growth Rate: Extremely Fast
Care Level: Very Easy
Lighting Requirements: Low to High
CO2 Requirements: Not required
Temperature: 60–82°F
pH Range: 6.0–8.0
Duckweed is recognized scientifically as the world's smallest flowering plant, with each individual plant measuring just a few millimeters across.
Duckweed is widely used in aquariums and aquaculture for its exceptional ability to absorb nutrients and improve water quality.
Benefits of Duckweed include:
Removes nitrates, ammonia, and phosphates rapidly
Provides shade and reduces algae growth
Excellent cover for shrimp, fry, and small fish
Nutritious food source for many herbivorous fish
Easy to propagate and maintain
Thrives in nearly any freshwater condition
Duckweed thrives under a wide range of lighting conditions. Because it floats at the surface, it receives maximum light exposure regardless of tank lighting intensity.
For best results:
Provide low to high aquarium lighting
Maintain a consistent photoperiod of 6–10 hours
Avoid excessive heat from light fixtures
Duckweed is one of the most light-tolerant floating plants available.
Duckweed does not require CO2 injection because it absorbs CO2 directly from the air.
Extremely fast growth
Suitable for all aquarium setups
No supplementation needed
No additional benefit
Atmospheric CO2 access already meets needs
Growth rate unchanged
Duckweed is one of the few plants that performs optimally without any CO2 supplementation.
Duckweed floats freely on the water's surface and does not require substrate. Its placement depends on water flow and surface conditions.
Placement recommendations include:
Keep in calm water areas
Avoid direct filter outflow
Use surface skimmers cautiously, as they remove Duckweed quickly
Provide adequate humidity above the water line
Floating rings can be used to contain Duckweed in a specific area of the tank.
To introduce Duckweed:
Rinse the plant gently in dechlorinated water
Place portions on the water surface
Spread evenly across the tank
Avoid submerging the leaves
Allow the colony to spread naturally
Within days, Duckweed will multiply rapidly and form a dense surface layer.
Duckweed grows extremely fast and requires regular thinning to prevent total surface coverage that blocks light to plants below.
Maintenance tips:
Skim the surface weekly to remove excess plants
Remove yellowing or waterlogged leaves
Maintain consistent humidity to prevent damage
Use a net to remove large quantities easily
Excess Duckweed can be fed to herbivorous fish, composted, or shared with other aquarists.
Duckweed pairs well with most peaceful freshwater species and is especially appreciated by fish that consume floating plants.
Compatible tank mates include:
Bettas
Goldfish (which often eat Duckweed)
Guppies
Shrimp
Mollies
Killifish
Many herbivorous fish will consume Duckweed faster than it can reproduce, providing natural population control.
The most common issue with Duckweed. Skim the surface regularly to prevent complete coverage that blocks light to other plants.
Indicates nutrient deficiency, particularly iron or nitrogen. Supplement with comprehensive liquid fertilizer.
Duckweed can easily transfer between tanks via nets, plants, or fish. Sanitize equipment to prevent unwanted spread.
Once established, Duckweed is notoriously difficult to fully eliminate. Use surface skimmers, nets, and herbivorous fish to control populations.
Duckweed is one of the most effective floating aquarium plants for nutrient absorption, surface shading, and providing cover for shrimp and fry. While its rapid growth requires regular management, it remains one of the easiest and most rewarding plants to grow in freshwater aquariums. With basic surface maintenance and stable conditions, Duckweed will quickly establish itself as a functional and attractive addition to any planted aquarium. Please remember to verify local regulations before purchasing Duckweed, as some states restrict its sale or possession due to its potential to escape into native waterways.
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