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.
Updated 1 min read
Part of our complete guide to aquatic mosses.
Moss
Riccia / Crystalwort
Riccia fluitans
Worldwide temperateAdvanced
TL;DR, Riccia / Crystalwort
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
Tank fit
The parameters that decide whether riccia / crystalwort fits in your tank.
Parameters
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Low
Medium
High
None
Optional
Recommended
Required
Slow
Medium
Fast
V. fast
Still
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Medium
High
V. high
Profile
Family
Ricciaceae
Type
Liverwort (treated as moss)
Attachment
Tied under mesh; floats otherwise
Typical use
Bright green carpets that pearl heavily
Trimming
Trim weekly, buoyant fronds break free if too long
Habitat
Calm sun-lit ponds and ditches worldwide
Worldwide temperate
Who it lives with
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Weighing it against something similar? Compare Riccia / Crystalwort head to head:
Pro tips
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.
Things to watch for
What can go wrong and how to spot it.
Things to watch for
Failure modes, in order of how dramatic the fix is.
Algae
Algae issues
Hair algae loves Riccia's fine surface. Stable CO₂ and proper light hours prevent it.
Common mistakes
Common mistakes
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).
How to care for it
The practical routine, read top to bottom.
Tying / attachment
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.
Tank setup
HIGH light, CO₂ REQUIRED to keep submerged form. Without these, Riccia floats and detaches. Trim weekly — long fronds catch buoyancy and break free.
Background
Where it comes from, how it behaves, and the variants you'll see at retail.
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In the wild
Where it lived before it came home.
Origin · Worldwide temperate
Floating freshwater liverwort distributed globally. Naturally a floating species, not a submerged plant.
Emersed form
Grows easily emersed as a floating cushion on damp soil.
Variants & identification
The named cultivars and the lookalikes worth flagging.
Variants
Standard R. fluitans.
Identification
Bright green forking branches in a tight cushion. No leaves — just branching thallus.
Sister species
Crystalwort (R. fluitans var.), R. rhenana. Many similar liverworts in the trade.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
How do you attach Riccia / Crystalwort in an aquarium?
Attachment: Tied under mesh; floats otherwise Typical aquascaping use: Bright green carpets that pearl heavily
Does Riccia / Crystalwort need CO₂?
CO₂: required. Light: high. Growth rate: fast.
What water parameters does Riccia / Crystalwort need?
Riccia / Crystalwort (Riccia fluitans) tolerates 20–26 °C and pH 6.0–7.5. Flow: low to medium.
How do you trim Riccia / Crystalwort?
Trim weekly, buoyant fronds break free if too long
Is Riccia / Crystalwort beginner-friendly?
Difficulty: 4/5. Advanced, demands dialled-in CO₂/dosing or precise water chemistry.
Sources & further reading
More mosses
See all mossesAdjacent specimens in the catalogue.
Cross-references
Build the rest of the tank.
A planted tank is a system. Pair this moss with one entry from each other pillar to plan the whole scape.
