Riccia fluitans
Riccia fluitans
Also known asCrystalwort · Floating crystalwort
Water parameters
Light and nutrients
Substrate type: floating. Propagation: fragmentation.
Substrate compatibility
| Substrate | pH effect | Nutrient load |
|---|---|---|
| Wood and rock mounts (Hardscape mount) | varies | none |
| Bare bottom (no substrate) (Bare bottom) | n/a | none |
| Inert sand (Pool filter sand) | neutral / inert | none |
| Inert gravel (Aquarium gravel) | neutral / inert | none |
| Aquasoil (ADA Amazonia) | lowers pH | very high |
| Mineralized clay substrate (Seachem Fluorite) | neutral / inert | moderate |
With fish
Origin and habitat
Distributed across tropical and temperate regions worldwide. The species (Riccia fluitans, commonly called crystalwort) is a liverwort that naturally floats on the water surface in ponds, ditches, and slow streams. The plant consists of branching, flat, bright green thalli (frond-like structures) that form tangled floating mats. Riccia gained fame in the aquascaping world through Takashi Amano's Nature Aquarium books, where he popularized the technique of tying Riccia to flat stones with hairnets or mesh, creating submerged 'Riccia stones' that pearl (produce visible oxygen bubbles) under high light, creating a sparkling, jewel-like effect. This pearling is one of the most visually spectacular phenomena in planted tanks. Riccia fluitans has been known to science since the 1700s as a common liverwort but only entered mainstream aquascaping through Amano's influence in the 1990s and 2000s. The pearling effect occurs because the thin thalli have a very high rate of photosynthetic oxygen production relative to their mass, and the water becomes locally supersaturated with dissolved oxygen, causing visible bubble formation on every surface.
Care notes
Naturally a floater, but most aquascapers grow it submerged by tying it to flat stones or mesh with hairnets, fishing line, or stainless steel mesh. Under high light with CO2, submerged Riccia grows rapidly and produces vigorous oxygen bubbles (pearling) during the photoperiod. The pearling effect is the primary reason keepers grow it; the tiny gas bubbles covering the bright green thalli sparkle under light. Maintaining Riccia submerged is high-maintenance: the plant is positively buoyant and constantly tries to float away. The inner portions of dense Riccia mats die and decompose, releasing the outer portions. Regular retying (every 2-4 weeks) is necessary. Without high light and CO2, submerged Riccia grows slowly and doesn't pearl impressively. As a floater, Riccia is easy and needs no special care: any light, any water chemistry, temperature 15–30°C. The floating form is useful for nutrient export and fry cover but not as visually dramatic. For the iconic pearling Riccia stones, expect: high light, CO2, weekly maintenance, and patience. Available from aquatic plant retailers and hobbyist trades.