Aquatic PlantsBeginner🌗 Medium light
Duckweed
Lemna minor · also called Common duckweed, Lesser duckweed, Water lentil
Generally non-toxic to cats and dogs.
Duckweed is a tiny, free-floating plant consisting of one to a few oval fronds with a single dangling root, forming dense green carpets on still water. It is one of the fastest-growing and most efficient nutrient-absorbing plants, but it spreads aggressively and is notoriously hard to remove.
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Quick facts
| Category | Aquatic Plants |
| Family | Araceae |
| Native origin | Cosmopolitan - native to temperate and tropical regions worldwide (Europe, Africa, Asia, the Americas) |
| Care difficulty | Beginner |
| Light | Medium light |
| Pet toxicity | Pet-safe |
Light
Grows under almost any light from low to very high; more light simply means faster, denser growth. It tolerates low light well but multiplies explosively under strong illumination. Because it covers the surface, it readily shades out plants below.
Water
Extremely tolerant: temp 6-33 C (43-91 F), pH ~5-9, soft to hard water. Acts as a heavy feeder that strips nitrate, phosphate and ammonia from the water column, making it useful for nutrient export. No special dosing needed; it thrives on fish waste. No CO2 injection required.
Soil & potting
Not an epiphyte and not rooted in substrate - it floats with a single short root hanging into the water and feeds directly from the water column. Never plant or bury it.
Environment — humidity, temperature, placement
No CO2 required (uses atmospheric CO2). Prefers still or very slow-moving water; in calm tanks it forms a complete surface mat. Strong surface flow and skimmers help corral or remove it. Purely floating and surface-emersed. Note that a full duckweed cover can block gas exchange and light, so thin it regularly.
Propagation
Reproduces almost entirely by vegetative budding - each frond buds off new fronds from lateral pouches, doubling its population in days. It rarely flowers. To propagate simply transfer a few fronds; to control it, net it out repeatedly.
Toxicity detail
Non-toxic and even edible/nutritious - many fish, turtles, and waterfowl eat it. The main hazard is invasiveness: it is regarded as a weed, can clog ponds and tanks, and is extremely difficult to eradicate once established (it hitchhikes on plants, nets and hands). Do not release into the wild; dispose of excess in the trash.
Growth stages
How this plant changes through its life — each stage often has its own care, diet and space needs.