Riccia
Riccia fluitans
Also sold as Crystalwort
Synonyms Riccia moss · Floating crystalwort
Riccia (Riccia fluitans) is a moss for the foreground and the surface, growing to about 3 cm (1.2 in) at a moderate pace. It wants 64–79°F (18–26°C), high light and CO₂ if you have it, and counts as a medium-difficulty plant to keep alive.
At a glance
| Type | Moss |
|---|---|
| Light | HighThe least light it survives in, not the light it looks best in. |
| CO₂ | RecommendedWhether it survives without added CO₂ — not whether CO₂ would help it grow faster. |
| Difficulty | Medium |
| Temperature | 64–79°F (18–26°C) |
| Max height | 3 cm (1.2 in)Grown submersed, left to mature, never trimmed. |
| Growth rate | Moderate |
| Placement | attached to rock or wood and floating |
| pH | 6–8 |
Before it goes in
- Riccia needs high light. A low- or medium-light LED is not enough for it to last.
- CO₂ is not required, but without it expect slow growth and a thinner result.
- Glue or tie it to rock or wood. Buried in the substrate the rhizome rots, which is the usual way Riccia is killed.
- It stays around 3 cm (1.2 in), low enough to keep the front glass clear.
Can it grow without CO₂?
Yes, but slowly. Riccia is listed as CO₂-recommended, not CO₂-required: without injection it survives and grows, it just takes far longer to fill in.
How much light does it need?
High light — and that is the survival line, not the “it looks better” line.
How big does it get?
About 3 cm (1.2 in) tall when it is mature and untrimmed, growing at a moderate pace, after roughly 2 weeks to root in.
Can I attach it to wood or rock?
Yes, and that is the only way to keep it. Glue or tie it down; buried in the substrate the rhizome rots.
What it goes with
- Plants that run on the same light and CO₂, so they can share a tank without one of them being the odd one out: Hygrophila corymbosa 'Siamensis', Water Sprite, Anubias nana 'Petite' and Cryptocoryne wendtii.
- Animals that share its temperature range and will not eat or uproot it: Betta, Cherry Shrimp, Angelfish and Bristlenose Pleco.
Often compared with
| Riccia | Fissidens fontanus | Christmas Moss | |
|---|---|---|---|
| Light | High | Medium | Low |
| CO₂ | Recommended | Recommended | Not needed |
| Max height | 3 cm | 3 cm | 4 cm |
| Difficulty | Medium | Medium | Easy |
More plants
Sources (4) · checked Sep 2026
- pH, Lightaquasabi.com
- CO₂tropica.com
- aquasabi.com
- flowgrow.de