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
A cosmopolitan thallose liverwort, Riccia fluitans, the floating crystalwort, family Ricciaceae in the order Marchantiales, found in ponds, ditches and slow streams across Asia, Europe, Africa and North America. Despite being filed with mosses in the trade, it is a liverwort, not a true moss, and it has no roots, stems or leaves, just branching flat bright-green thalli that tangle into floating or submerged mats. It is amphibious, growing both in water and on damp ground. It became an aquascaping icon through Takashi Amano, who tied it over flat stones with hairnets to make submerged 'Riccia stones' that pearl, throwing off streams of oxygen bubbles under strong light for a sparkling, jewel-like effect, one of the most spectacular sights in a planted tank. The pearling happens because the thin thalli photosynthesise so fast for their mass that the surrounding water goes locally supersaturated with oxygen and bubbles form on every surface.
Care notes
By nature a floater, but most aquascapers grow it submerged by tying it over flat stone or mesh with hairnet, line or stainless mesh, since it does not attach on its own. Submerged it needs bright light and CO2 to grow fast and pearl impressively, and the pearling is the whole point. Keeping it down is high-maintenance: it is buoyant and always trying to float free, and the inner part of a thick mat dies and rots, freeing the outer layer, so it must be re-tied every few weeks. Without strong light and CO2 the submerged form grows slowly and barely pearls. As a floater it is effortless, taking any light, any water chemistry and a wide temperature range, useful for nutrient export and fry cover but far less dramatic. For the iconic pearling Riccia stone, plan on high light, CO2, weekly upkeep and patience. It is an ornamental liverwort, not a crop, so it is unsuited to media-bed aquaponics or hydroponics.