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Spirodela Polyrhiza
Spirodela polyrhiza
📍 Cosmopolitan; native across temperate and tropical regions of North America, Europe, Asia, Africa, and Australia in still or slow-moving freshwater bodies
Spirodela polyrhiza, commonly known as giant duckweed, is a small floating plant with round to oval fronds measuring 5-10mm, distinguished by multiple dangling roots beneath each frond and a reddish-purple underside. It forms a dense surface mat that provides excellent shade, reduces algae by outcompeting it for nutrients, and offers refuge for surface-dwelling fish and fry. In the aquascape it serves as a natural nutrient export, biological filter aid, and aesthetic top layer that softens harsh lighting.
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Tanks keeping this 🌿
Growing in 2 tanksCommunity tanks featuring Spirodela Polyrhiza.
Compatible Livestock
Common Diseases
Yellowing / Nitrogen Deficiency
Fronds turn pale yellow or white, growth slows significantly
Increase water column nutrients via liquid fertilizer (especially nitrogen); ensure adequate fish load or supplement with nitrate dosing
Algae Overgrowth on Fronds
Green or brown film coating fronds, fronds sink or clump together
Increase surface agitation slightly to keep fronds moving; reduce excess nutrients and lighting duration; manually remove affected fronds
Melt / Frond Deterioration
Fronds become translucent, mushy, or disintegrate; rapid die-off of the colony
Check for sudden temperature swings, salt additions, or copper-based medications which are lethal to duckweed; stabilize water parameters and remove dead material promptly
Overcrowding / Oxygen Depletion
Dense mat blocks all light to lower plants; fish gasp at surface due to reduced gas exchange
Manually thin the colony regularly, removing 30-50% of fronds weekly; use a floating ring to limit spread to a portion of the surface
Tips from the community 💡
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Quick Facts
- co2
- Not required
- light
- Low to Medium (20-80 PAR); thrives under moderate light but tolerates low light with slower growth
- placement
- Surface floating; not planted — fronds drift freely or can be corralled with a floating ring to control spread
- substrate
- Not planted in substrate (free-floating; absorbs nutrients directly from the water column)
- growth rate
- Fast
- propagation
- Vegetative budding; daughter fronds bud off from the parent frond and separate, rapidly doubling the colony under good conditions
Water it likes
- ph
- 6.0-8.0
- hardness
- 2-20 dGH
- temperature
- 50–86°F (10–30°C)
Legality
No state or federal restrictions on record for this species.
Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.