TankBud

Watermeal

Wolffia globosa

Also known as Asian watermeal, Water meal

FreshwaterFloatingPlantlets

Invasive. Watermeal spreads explosively and is invasive outside its native range. Never release into the wild; dispose of in the trash.

Watermeal (Wolffia globosa)
(c) chiuluan, some rights reserved (CC BY) · cc-by

Care at a glance

Light
Medium light
CO2
No CO₂ needed
Temperature
64–86°F
18–30°C
Max height
0 in
0.1 cm
Growth rate
Fast
Placement
Floating
Type
Floating
pH
6.0–7.5
Hardness
3–20 dGH
Spread
39.4 in (100 cm)
Nutrient uptake
Water column
Growth region
Submersed or emersed
Difficulty
Easy
Family
Araceae
Origin
Southeast Asia

Overview

Watermeal is an easy, fast-spreading surface floater for warm-water tanks.

Did you know

Watermeal produces the world's smallest fruit. People in parts of Southeast Asia eat it as a protein-rich vegetable called khai-nam, or water eggs.

Caring for watermeal

Watermeal floats on the surface and takes its nutrients straight from the water. It needs medium light and no CO2, and it soaks up nutrients like a sponge. It suits warm water from 64 to 86°F (18 to 30°C).

Keep surface flow gentle, or it gets sucked into filters and pushed around. It grows fast and shades the tank below, so skim it off regularly. It reproduces almost entirely by budding, and a culture can double its mass in two to four days.

Shrimp, snails and small fish eat it as a live food. Its speed makes it a nuisance if you let it take over. It is invasive outside its native range, so never release it into the wild.

Good to know

Watermeal, Wolffia globosa, is the world's smallest flowering plant, with each frond about 0.1 to 0.2 mm across. It sits in the duckweed subfamily Lemnoideae within the arum family, Araceae. It has no roots, stems or true leaves, just a single tiny floating thallus shaped like a green ball.

In the wild

Watermeal is native to Southeast Asia, where it floats in dense green films on calm ponds, ditches, marshes and slow backwaters. Given nutrients and warmth, it blankets still water quickly. It has become naturalized and invasive well beyond its native range, including parts of Europe and North America.

Common questions

Does watermeal need to be planted in the substrate?

No. Watermeal floats at the surface and takes its nutrients straight from the water.

Does watermeal need CO2?

No. Watermeal grows well without added CO2.

How much light does watermeal need?

Watermeal wants medium light. A light sold for planted tanks covers it.

How do you propagate watermeal?

Watermeal propagates by plantlets. Plantlets bud from the parent and drift off.

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