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Giant Duckweed (Spirodela polyrhiza)

Giant Duckweed is the larger cousin of common duckweed, with rounder fronds up to about a quarter inch across and several trailing roots beneath each, making it easier to net out than tiny Lemna. It is an extremely fast floating nutrient sponge that shades the tank and helps fight algae, needing no CO2 and almost any light. The trade-off is its speed: it can blanket the surface in days and is very hard to fully remove once introduced.

Care specifications

TypeFloating
DifficultyEasy
LightLow (20–100 µmol PAR)
CO2Not needed
Fertilizer demandLow
Growth rateFast
Max height1 in
Spread1 in
PlacementFloating
Attaches to hardscapeNo
Snail & shrimp safeYes
Temperature64–86 °F
pH6–7.5
ColorGreen
TrimmingFrequent
StylesJungle, Biotope, Nature

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Giant Duckweed

Giant Duckweed (Spirodela polyrhiza)

$7.99 Out of stock

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Propagation

Each frond buds off new fronds continuously, so it doubles its surface coverage rapidly without any intervention.

Frequently asked questions

Is Giant Duckweed easier to control than regular duckweed?

Somewhat. Its larger fronds and multiple roots make it easier to scoop out by hand or net than the tiny single-rooted common duckweed, but it still grows explosively and a few leftover fronds will repopulate the surface.

Will Giant Duckweed block light from my other plants?

It can. A thick surface mat shades plants below and may starve light-hungry species, so skim off a portion regularly to keep coverage partial. Many keepers run it deliberately in low-light or betta tanks where the shade is welcome.

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