Giant duckweed

Spirodela polyrhiza

Also known as Greater duckweed, Great duckweed, Common duckmeat, Lemna polyrhiza

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Giant duckweed (Spirodela polyrhiza) — Stefan.lefnaer · CC BY-SA 4.0

Care at a glance

Light: Low light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Floating
Type: Floating
Temperature: 59–82°F (15–28°C)
pH: 6.0–8.0
Hardness: 2–18 dGH
Max height: 0.4 in (1 cm)
Spread: 11.8 in (30 cm)
Nutrient uptake: Water column
Growth region: Submersed or emersed
Difficulty: Easy
Origin: A free floating duckweed found on still and slow fresh water across most of the world, forming green films on sheltered ponds and backwaters.
Family: Araceae

Overview

Just float it on the surface in low to moderate light, with no CO2 or substrate needed. It soaks up nitrate and phosphate quickly, which makes it useful for controlling nutrients, but it also shades the tank and clogs filters, so skim off the excess often. Be aware that a few fronds are almost impossible to fully remove once introduced.

In the wild

Giant duckweed is the larger cousin of common duckweed, with rounded green fronds up to about a centimeter across. The top is bright green while the underside often shows a reddish purple tint, and each frond trails a small cluster of roots. It floats and multiplies fast, forming a living blanket across calm water.

Good to know

Duckweeds are among the smallest and simplest flowering plants, reduced to a flat frond and roots with rarely seen tiny flowers. Spirodela polyrhiza is set apart from Lemna by carrying many roots per frond instead of a single one.

Did you know

When conditions turn cold it makes dense starch filled buds called turions that sink to the bottom to overwinter, then rise and sprout again in spring.