Duckweed (Lemna minor) care guide

Group
Plants
Other names
Common duckweed, Lesser duckweed
Family
Araceae (arum family; formerly Lemnaceae)
Origin
Most of Africa, Asia, Europe and North America; naturalised in Australasia and South America
Water
freshwater
Maximum size
0.8 cm
Temperature
6–33°C
pH
6.5–8
Care level
beginner
Lighting
Medium to high light; CO2 not needed
Flow
Still water; strong surface flow breaks it up

Care

Common duckweed is the familiar floating plant of ponds and ditches. Each oval frond is 1–8 mm long with a single root 1–2 cm long. It grows at about 6–33 °C and does best at pH 6.5–8. In cold weather it forms dormant, starch-filled buds that sink and sit out the winter. In aquariums duckweed shades the tank, mops up nitrate and phosphate, and feeds herbivorous fish, but it spreads fast and is very hard to get rid of. Scoop out the surplus every week or two and keep it away from strong surface flow, which pushes it into heaps and filter intakes. It is grown commercially as protein-rich animal and fish feed and for cleaning wastewater, and it is a favourite live food for goldfish and other herbivores. It suits ponds, coldwater and tropical tanks alike. Birds carry it between waters on their feet and feathers. Sources: Wikipedia (en.wikipedia.org/wiki/Lemnaminor); Wikipedia (en.wikipedia.org/wiki/Lemna); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

Spreads by budding: each frond produces daughter fronds that break away, so a few fronds soon cover the surface in good light and nutrients. Flowers and seeds are rare in tanks.

Compatibility and tank mates

Goldfish, koi, silver dollars, many cichlids and some gouramis eat duckweed eagerly, which can keep it in check. It suits fry, betta and shrimp tanks, but it clogs filter intakes and is very hard to remove completely once introduced, so think before adding it to a display tank.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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