How do you grow Riccia fluitans in an aquarium? Float Riccia fluitans at the surface or tie thin pads to stone or wood with fishing line. Give it medium light and, ideally, added CO2. Tropica rates it medium for light and CO2, and Dennerle lists 64 to 82°F (18 to 28°C) and pH 5 to 8. Trim it often, because new shoots always grow upward.
Key takeaway: Riccia fluitans (crystalwort) is a cosmopolitan liverwort that floats or can be tied down as a bright green foreground cushion. Tropica says it grows 0.4–2 in (1–5 cm) tall, thrives best with added CO2 and pearls oxygen bubbles in good conditions. Dennerle lists 64–82°F (18–28°C), pH 5–8, very soft to hard water and propagation by division. Expect regular trimming and re-tying.
| Fact | What sources report | Source |
|---|---|---|
| Type | Liverwort (crystalwort), cosmopolitan | Tropica, Dennerle |
| Height | 0.4–2 in (1–5 cm) | Tropica, Dennerle |
| Light | Medium (Tropica); medium–low (Dennerle) | Tropica, Dennerle |
| CO2 | Medium, 6–14 mg/L (Tropica); 0–10 mg/L (Dennerle) | Tropica, Dennerle |
| Temperature | 64–82°F (18–28°C) | Dennerle |
| pH and hardness | pH 5–8; very soft to hard | Dennerle |
| Growth rate | Medium (Tropica); fast (Dennerle) | Tropica, Dennerle |
What Is Riccia Fluitans?
Riccia fluitans is a small thalloid liverwort, often sold as a moss and commonly called crystalwort. Tropica describes it as a cosmopolitan liverwort 0.4 to 2 inches (1 to 5 cm) tall, and Dennerle notes it is documented around the world, floating on the surface or living on moist substrate. It forms dense mats of narrow, forked, bright green branches.
Both companies credit Japanese aquascaper Takashi Amano with popularizing it. He used it tied to stones as a lush foreground in many layouts, which is still the classic look. Because it has no true roots, it never anchors itself as firmly as mosses such as Java moss, or rhizome plants like Java fern.
- As a floater: shades the tank and shelters fry.
- Tied down: forms a bright foreground cushion.
- On mesh or stone: easy to move during maintenance.
How Do You Grow Riccia Fluitans in an Aquarium?
Decide first whether it will float or sit on hardscape. As a floating plant, Tropica says it offers good protection for young fish. To use it as a carpet, tie a thin layer onto a flat stone, slate or stainless mesh. Tropica notes it can be kept down with fishing line, and Dennerle suggests attaching cushions to rocks or logs.
- Rinse the portion and remove snails, algae and loose debris.
- Spread a thin, even layer about 1/4 inch (6 mm) thick on the stone.
- Wrap fishing line or cotton thread tightly across it in a grid.
- Place the stone in the foreground under medium light.
- Re-tie or replace the line every few weeks as the pad thickens.
Keep layers thin. When the pad gets thick, the lower branches lose light, die and break loose, and whole sections float up.
What Light Does Riccia Fluitans Need?
This liverwort does best in medium light. Tropica rates its light demand as medium, which it defines as about 0.5 W/L, while Dennerle lists medium to low. In practice, pieces near the surface get plenty of light, while tied-down pads need a stronger LED to stay compact and avoid looking pale or stringy.
Run lights for 7 to 8 hours a day to start. If algae begins to grow inside the pad, reduce the photoperiod before you cut fertilizer, because algae in fine branches is very hard to remove later. Our black beard algae guide covers the worst offenders.
Does Riccia Fluitans Need CO2 and Fertilizer?
CO2 is strongly recommended for a carpet. Tropica says the plant thrives best with added CO2 and rates its need as medium, 6 to 14 mg/L. Dennerle lists 0 to 10 mg/L and says CO2 significantly increases growth. Floating portions can survive without it, but a tied-down carpet usually stays dense only when CO2 is added.
In good conditions small oxygen bubbles form on the leaf tips, Tropica notes, which is a sign the plant is photosynthesizing strongly. Feed with a balanced liquid fertilizer, since the plant takes nutrients from the water column. See aquarium CO2 for plants and aquarium plant fertilizer.
- CO2: 6–14 mg/L is Tropica’s medium range.
- Fertilizer: liquid, dosed lightly and often.
- Root tabs: not needed; it has no roots in the substrate.
What Water Parameters Does Riccia Fluitans Like?
Crystalwort adapts to most tropical tanks. Dennerle lists water temperatures of 64 to 82°F (18 to 28°C), pH 5 to 8 and very soft to hard water. That covers most community, shrimp and planted tanks. Stable conditions matter more than exact numbers, so avoid large swings during water changes.
- Temperature: 64–82°F (18–28°C).
- pH: 5–8.
- Hardness: very soft to hard.
- Flow: gentle; strong currents shred floating mats.
How Do You Trim and Propagate Riccia Fluitans?
Trim often and propagate by division. Tropica says new shoots always grow toward the surface, so it may be necessary to prune with scissors, and Dennerle recommends trimming the light green branches every so often to keep growth compact. Every clipping can become a new plant, which is why Dennerle lists division as its propagation method.
- Lift the stone out or trim it in place with curved scissors.
- Cut the top layer evenly, like mowing a lawn.
- Net out every floating piece so it does not clog filters.
- Tie the healthiest clippings onto a new stone.
Some aquarists treat it as invasive in display tanks, because stray bits get everywhere. A surface skimmer or a fine net makes clean-up easier.
Why Is Riccia Fluitans Melting or Not Growing?
The usual causes are low light, no CO2, thick pads and algae. A tied pad that gets too thick turns brown underneath and floats loose. Low CO2 makes growth thin, and too much light without CO2 grows algae on the pad. Thin the pad, fix lighting and CO2, and re-tie fresh growth.
- Brown base: pad too thick; trim and re-tie.
- Floating up: line loosened or base died; re-tie.
- Stringy, pale growth: more light or CO2 needed.
- Algae on pads: cut photoperiod and fertilizer slightly.
If you would rather avoid tying, try true carpets such as Monte Carlo or dwarf hairgrass, or keep it floating with other floating plants for aquariums.
FAQ About Riccia Fluitans
Is Riccia fluitans a moss?
No, it is a liverwort, though it is sold alongside mosses.
Does Riccia fluitans need CO2?
Not to survive floating, but carpets grow best with CO2.
How tall does crystalwort grow?
About 0.4–2 inches (1–5 cm).
Can crystalwort attach on its own?
No, it must be tied to stone, wood or mesh.
Is Riccia good for shrimp tanks?
Yes; it gives shelter and grazing surface.
What temperature does Riccia fluitans need?
64–82°F (18–28°C), per Dennerle.
Sources
- Tropica Aquarium Plants — Riccia fluitans plant info/4386)
- Dennerle Plants — Riccia fluitans plant profile/23036)
- Photo credits (Wikimedia Commons, edited with titles): Riccia fluitans kz1 by Krzysztof Ziarnek, Kenraiz (CC BY-SA 3.0); Riccia fluitans 1 (Piotr Kuczynski) by Piotr Kuczynski (CC BY-SA 3.0)