Riccia fluitans
Amano popularised it as a substrate carpet, but it has no roots, so it must be tied under stainless mesh. Pearls oxygen aggressively under CO₂ and high light.
Riccia / Crystalwort (Riccia fluitans) is a liverwort (treated as moss) aquatic moss native to Worldwide temperate. Light: high. CO₂: required. Growth rate: fast. Target 20–26 °C and pH 6.0–7.5. Attach via tied under mesh; floats otherwise. Typical use: bright green carpets that pearl heavily. Trimming: Trim weekly, buoyant fronds break free if too long
Care at a glance
Amano popularised it as a substrate carpet, but it has no roots, so it must be tied under stainless mesh. Pearls oxygen aggressively under CO₂ and high light.
By Mike ElmiraUpdated 1 min read
Part of our complete guide to aquatic mosses.
The parameters that decide whether riccia / crystalwort fits in your tank.
Ricciaceae
Liverwort (treated as moss)
Tied under mesh; floats otherwise
Bright green carpets that pearl heavily
Trim weekly, buoyant fronds break free if too long
Calm sun-lit ponds and ditches worldwide
Worldwide temperate
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Hard-won lessons from the tank.
Takashi Amano popularised it as a substrate moss — but it's high-effort. Pearling under CO₂ is unmatched: each frond becomes a tiny oxygen bubble factory. If you're not running CO₂, skip Riccia and pick Java instead.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Hair algae loves Riccia's fine surface. Stable CO₂ and proper light hours prevent it.
1) Trying to keep it submerged without CO₂ — it floats away. 2) Not trimming — long fronds break off and become floating debris. 3) Confusing with Süßwassertang (which is actually a fern).
The practical routine, read top to bottom.
Wrap under stainless steel mesh (sold as 'Riccia mesh') and weight to bottom. Without mesh, it floats. Cyanoacrylate to stone also works but the mesh is more secure.
HIGH light, CO₂ REQUIRED to keep submerged form. Without these, Riccia floats and detaches. Trim weekly — long fronds catch buoyancy and break free.
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
Floating freshwater liverwort distributed globally. Naturally a floating species, not a submerged plant.
Grows easily emersed as a floating cushion on damp soil.
The named cultivars and the lookalikes worth flagging.
Standard R. fluitans.
Bright green forking branches in a tight cushion. No leaves — just branching thallus.
Crystalwort (R. fluitans var.), R. rhenana. Many similar liverworts in the trade.
Direct answers to the questions search engines and AI assistants surface most often about this species.
Attachment: Tied under mesh; floats otherwise Typical aquascaping use: Bright green carpets that pearl heavily
CO₂: required. Light: high. Growth rate: fast.
Riccia / Crystalwort (Riccia fluitans) tolerates 20–26 °C and pH 6.0–7.5. Flow: low to medium.
Trim weekly, buoyant fronds break free if too long
Difficulty: 4/5. Advanced, demands dialled-in CO₂/dosing or precise water chemistry.
A planted tank is a system. Pair this moss with one entry from each other pillar to plan the whole scape.
