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Riccia fluitans

Also known as Crystalwort, Floating crystalwort, Floating liverwort, Riccia

FreshwaterMossFragmentationDivision

Invasive. Can form weedy floating mats and is regulated in some regions. Never release into the wild; dispose of in the trash.

Riccia fluitans (Riccia fluitans)
Piotr Kuczynski · CC BY-SA 3.0

Care at a glance

Light
High light
CO2
CO₂ beneficial
Temperature
59–86°F
15–30°C
Max height
1.2 in
3 cm
Growth rate
Fast
Placement
Floating
Type
Moss
pH
6.0–8.0
Hardness
0–21 dGH
Spread
15.7 in (40 cm)
Nutrient uptake
Water column
Growth region
Submersed or emersed
Difficulty
Medium
Family
Ricciaceae
Origin
Cosmopolitan (worldwide temperate and tropical fresh waters)

Overview

Riccia fluitans is a fast-growing floating liverwort that can also be grown as a submersed carpet. It is rated medium in difficulty.

Did you know

Aquascaper Takashi Amano popularized Riccia carpets by pinning the floating liverwort underwater. The result was the famous shimmering pearling lawns covered in oxygen bubbles, a use the plant never has in nature.

Caring for Riccia fluitans

Riccia fluitans is easy left floating, and it spreads fast. For a submersed carpet, pin a thin layer under mesh or hairnet onto hardscape. It constantly tries to detach and float free, so it takes more upkeep than typical carpets.

It needs high light and feeds from the water, so use a liquid fertilizer. It grows without injected CO2, but CO2 speeds it up, and a carpet under strong light and CO2 pearls heavily. It handles 59 to 86°F (15 to 30°C).

Trim it regularly. It traps fine debris, and it grows fast enough to shade plants below or clog filter intakes if it escapes. Pull clumps apart to spread it.

It spreads aggressively and is a recognized weedy, invasive nuisance in some regions. Never release it into local waterways.

Good to know

Riccia fluitans is a thalloid liverwort in the family Ricciaceae, part of the Marchantiophyta, though the hobby groups it with mosses. It has no true roots, stems or leaves, and the whole plant is a branching, ribbon-like green thallus. It reproduces almost entirely by fragmentation, with each broken piece growing into a new plant.

In the wild

Riccia fluitans is a cosmopolitan aquatic liverwort, floating in still and slow fresh water across temperate and tropical regions. In the wild it drifts at the surface as tangled mats. Only certain regional varieties, notably the Japanese form, adapt well to growing fully submersed.

Common questions

Does Riccia fluitans need to be planted in the substrate?

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

Does Riccia fluitans need CO2?

No, but it helps. Riccia fluitans can grow without injected CO2, and added CO2 makes it grow faster.

How much light does Riccia fluitans need?

Riccia fluitans needs high light from a strong planted-tank LED.

How do you propagate Riccia fluitans?

Riccia fluitans propagates by fragmentation and division. Pieces that break off keep growing, so pulling a clump apart spreads it. Each plant buds off new ones, so a few soon cover the surface.

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