Photo: Wikimedia Commons / CC BY-SA 3.0

Common Duckweed Care

Lemna minor · Araceae

🐾 Pet-safe 🎯 Easy ☀️ Full sun 💧 Every 7 days

🕮 5 min read 🕓 Last reviewed: 2026-08-23

Care at a glance

Light

Full sun

Temperature

6–33 °C (43–91 °F)

Soil

grows in water with pebbles, or a well-draining mix

Difficulty

Easy

Mature size

1–5 cm (0–2 in)

Pet safety

Pet-safe

Care effort Medium

The short version

Beginner-friendly and forgiving.
Give it Full sun.
Water every 7–7 days.
Safe around cats and dogs.

The Common Duckweed (Lemna minor) is an aquatic plant grown submerged in freshwater aquariums. It comes from Worldwide and is rated Easy to keep, reaching 1–5 cm. Here is how to grow it underwater — lighting, substrate, CO₂, placement and propagation.

Also known asLemna minorアオウキクサ浮萍Lenteja de aguaLentille d'eau

📋Quick facts

Growth rate	Fast
Mature size	1–5 cm (0–2 in)
Native region	Worldwide
Plant family	Araceae
Toxicity	Non-toxic
Air-purifying	No
Ideal for	beginners, homes with pets

⚖️Pros & cons

Pros

Non-toxic to cats and dogs
Hard to kill; great for beginners
Fast, rewarding growth
Compact — fits a desk or shelf

Cons

Needs high humidity to look its best
Needs a bright, sunny spot

🐟Growing it in an aquarium

Keep the water at 6–33 °C. Stable, gently moving water and regular partial water changes keep it healthy; sudden swings in temperature or chemistry cause melting.

Light

Give it Full sun-equivalent aquarium lighting. Low-tech tanks suit undemanding species; brighter light (and often CO₂) brings out the best colour and compact growth but also feeds algae, so balance it carefully.

Soil

Plant it in grows in water with pebbles, or a well-draining mix. Rooted species are hungry feeders — use root tabs or a liquid aquarium fertiliser (and CO₂ for demanding types). Epiphytes like Anubias, Java fern and Bucephalandra must NOT be buried: tie or glue their rhizome to wood or rock, or they rot.

Its size and habit suit a spot in the foreground, midground or background depending on how tall it grows; trim and replant tops to keep it dense.

✂️How to propagate, step by step

Spring and early summer, during active growth, give the best success. Here is how to do it, step by step:

division at repotting

Water the plant the day before to reduce stress on the roots.
Slide it out of its pot and gently shake off the loose soil.
Tease the root ball into sections, each with healthy roots and a few shoots.
Pot each section into fresh mix at its original depth.
Water them in and keep out of direct sun for a week while they recover.

🔬Classification

Plant type	Aquatic plant
Genus	Lemna
Family	Araceae · Araceae
Native to	Worldwide

🩺Common problems

Symptom	Likely cause	What to do
Algae on leaves or glass	Too much light or excess nutrients in the water	Cut the lighting period, reduce feeding, and add algae-eating clean-up crew.
Yellowing leaves	Usually overwatering or poor drainage	Let the soil dry more between waterings and make sure the pot drains.

🩺 Plant Doctor →

🐛Pests & prevention

The usual indoor pests are spider mites (fine webbing, speckled leaves), mealybugs (white cotton-wool tufts), scale (small brown bumps), and fungus gnats (tiny flies from soggy soil). Inspect any new plant before it joins the others, wipe the leaves now and then, and let the topsoil dry to keep gnats away. At the first sign, isolate the plant, wipe or rinse off what you can, and treat with insecticidal soap or neem oil every week until it is clear.

🐾Is it safe for pets?

Good news for pet owners: the Common Duckweed is considered non-toxic to both cats and dogs by the ASPCA. It is one of the safer choices for homes with animals, though eating any plant can still cause mild stomach upset.

Toxicity information is a general guide based on ASPCA data. If your pet or child may have eaten any part of a plant, contact a vet or poison control right away.