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Duckweed Overview

Scientific Name: Lemna minor
Common Name(s): Duckweed, Water Lens
Origin: Worldwide (native to freshwater ponds and slow-moving waters)
Plant Type: Floating Plant
Typical Height: 1–5 mm (individual fronds); forms dense mats
Difficulty Level: Easy
Lighting Requirements: Low to Medium
Temperature: 15–30°C

Duckweed is a tiny, free-floating aquatic plant known for forming dense, bright green mats on the surface of freshwater tanks and ponds. Its rapid growth and small, rounded leaves make it a natural oxygenator and algae competitor, which is why it’s popular in aquariums and aquaponics systems. Duckweed’s subtle yet effective coverage creates shade for fish and invertebrates while adding a natural, pond-like aesthetic

Aquarium Requirements for Duckweed

Lighting Requirements: Low to Medium – Duckweed grows well under standard aquarium lighting; brighter light encourages denser growth.

Temperature Range: 15–30°C – Tolerates a wide range, ideal for both tropical and temperate tanks.

pH Range: 6.0–8.0 – Very adaptable to different water conditions.

Placement in the Tank: Surface – Duckweed floats freely and can cover the water’s surface completely, providing shade for fish.

Growth Rate: Fast – Under optimal conditions, Duckweed can double in coverage within 2–5 days.

Tips for Success:

  • Fertilisation: Absorbs nutrients directly from the water; additional liquid fertilizers can boost growth in nutrient-poor tanks.

  • CO₂: Not required – Duckweed thrives naturally without supplementation.

  • Tank Considerations: Regular thinning is necessary to prevent blocking light for submerged plants.

Growth and Appearance

Duckweed consists of small, oval-shaped green fronds, each usually 1–5 mm across, often with tiny roots hanging below. When grown densely, it forms a continuous green carpet over the water surface, creating natural shade and shelter for aquarium inhabitants. Its tiny size and vibrant green color add a gentle, floating texture, contrasting beautifully with taller stem plants and midground species.

Care and Maintenance

Duckweed is extremely low-maintenance but benefits from routine monitoring:

  • Thinning: Remove excess mats weekly to prevent blocking light to lower plants.

  • Water Stability: Maintains well in varied water conditions but thrives in nutrient-rich, slightly filtered water.

  • Other Tips: Can be used as a natural food source for some fish and shrimp. Be cautious in heavily planted tanks, as it can overshadow slower-growing plants.

Aquascaping with Duckweed

Duckweed works best as a floating surface plant, ideal for nano tanks, ponds, and aquaponic systems. Its floating mats provide natural shade and reduce algae growth by limiting light penetration. Duckweed pairs well with taller stem plants and hardscape features, creating depth and a natural, layered effect in the aquarium. It also adds a dynamic, constantly changing element as the fronds drift with water currents.

Duckweed at Smiths Aquatics

At Smith’s Aquatics in Stockton-on-Tees, we regularly stock a variety of live aquarium plants, including Duckweed.

Our team can help you with:

  • Choosing suitable plants for your aquarium

  • Advice on lighting and plant nutrition

  • Selecting plants compatible with your fish and setup

  • Creating balanced planted aquariums

Visit our store to explore our current selection of live aquarium plants and find the right species for your aquarium.