Watermeal care guide
Watermeal (Wolffia arrhiza) — medium light, 18-28 °C, pH 6-8, no CO2.
Compiled by Aquairi from published sources · Published · Updated
Overview
Watermeal (Wolffia arrhiza) is an aquatic plant of the family Araceae, listed in the Aquairi knowledge base as a beginner-level species. It is typically grown under medium light and without obligatory CO2 injection on any substrate. Smallest flowering plant in the world — tiny green grains floating at the surface. Multiplies very fast and can be a nutritious live food for many fish, but tricky to remove once established.
Taxonomy
- Family: Araceae
- Genus: Wolffia
- Scientific name: Wolffia arrhiza
- Common synonyms: Mosquito Fern
Habitat
Wolffia is a genus of the smallest flowering plants on Earth (Araceae, duckweed subfamily), rootless floating grains found on still fresh waters worldwide. In the Aquairi knowledge base, populations associated with this form are recorded from Cosmopolitan.
Growth requirements
- Lighting: medium
- CO2: not required
- Temperature: 18-28 °C (64-82 °F)
- pH: 6-8
- GH: 3-16 °dGH
- Substrate: any
- Maximum height: 1 cm
- Growth rate: fast
- Recommended placement: floating
Placement
A microscopic floating plant that forms a fine green film on the surface; used mainly for nutrient export and as live food. In the Aquairi knowledge base this form is recommended for the floating layer under medium light and without obligatory CO2 injection, using any substrate.
Propagation
Reproduces almost entirely by budding, with each grain splitting to form a new plant; populations grow extremely fast. Documented propagation techniques for this entry include: adventitious plantlets on flower stalks.
Common issues
The tiny fronds are very hard to remove once spread and can fully cover the surface, blocking light; frequent skimming is required.
Propagating Watermeal (Wolffia arrhiza)
Overview
Wolffia arrhiza, known as watermeal, is the smallest vascular flowering plant on Earth. Each individual is a rootless, roughly spherical green frond about 1 mm wide with a flat top that lets it float at the water surface. It thrives in quiet, still water and behaves as a mixotroph, gaining energy from photosynthesis or by absorbing dissolved carbon from the water.
Propagation Method
Watermeal propagates almost entirely by vegetative budding rather than from cuttings or seed. The rounded body of each grain buds off a new individual, and this division repeats continuously. Under good conditions the population can double in less than four days, forming a dense floating mat over the surface.
Step-by-Step
- Start with a small clean clump of healthy floating grains skimmed from an established surface.
- Place the grains on the surface of still or very gently moving water so they can float freely.
- Provide medium light and a few free nutrients; the grains begin budding daughter individuals on their own.
- Allow the mat to spread; harvest or thin a portion every 3 to 4 days as the colony doubles.
- Move skimmed grains to a new container or tank to establish a fresh culture.
Conditions for Healthy Growth
- Temperature 18-28 C; in cooler water the plant goes dormant and sinks to overwinter.
- Medium lighting at the surface.
- Calm, still water with little surface agitation.
- Low nutrient demand; a small amount of dissolved nutrients is enough.
- No CO2 supplementation required.
Maintenance
Because the mat doubles every few days, skim and remove excess grains roughly weekly to keep light reaching plants below. Harvested watermeal is highly nutritious and can be fed to many fish, which also helps keep the colony in balance.