Riccia fluitans (crystalwort) care

Light

In the wild riccia fluitans grows on the bright edge of a forest canopy, not in the canopy and not in the open. Indoors, that translates to within a metre of an unobstructed window, sheer curtain optional. Needs high aquarium lighting to grow as a tight, pearling carpet. Under weak light it loosens, grows pale and floats apart rather than staying dense and compact. The fastest test: a hand held at the leaf casts a soft-edged shadow at noon — sharp shadow means too much sun, no shadow means too little light.

Watering

Aim for fully submerged or floating; 25-50% water change weekly for riccia fluitans, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Grown either floating at the surface or pinned submerged under mesh. Prefers clean, soft to moderately hard water with pH around 6-7.5; weekly partial changes keep it bright and healthy.

Soil and pot

Riccia fluitans grows best in none — floats or is pinned to hardscape. Rootless with no anchoring rhizoids; it must be trapped under mesh or netting against wood or stone to form a submerged carpet, otherwise it floats free at the surface. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Riccia fluitans sits happiest at around 100% (submerged or floating aquatic) humidity and 18-28°C (64-82°F). An aquatic liverwort living at or under the water surface, so room humidity is irrelevant. It can also be grown emersed in very humid setups as a low ground cover. If you keep the room above 18 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed riccia fluitans sparingly. Strongly responsive to CO2, which drives the pearling, oxygen-bubbling carpet; pair with a complete liquid fertiliser for fast, dense growth. Without CO2 and high light it grows loose and pale. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on riccia fluitans in the Growli community. Each is annotated with the most common cause so you know where to start.

• Floating free — Being rootless, it constantly tries to detach and rise; secure it under mesh or fine netting and re-pin escaping clumps to keep the carpet intact.
• Lower-layer die-off — As the mat thickens, shaded lower layers die and release the whole patch from its mesh; trim thin regularly so light reaches the base.
• Pale, loose growth — Insufficient light or CO2 makes it grow sparse and pale rather than pearling; increase lighting and inject CO2 for dense green growth.
• Algae and detritus — Dense tangles trap debris and host algae; maintain flow, trim often and keep nutrients balanced.

Propagation

Propagate by dividing the mat — any fragment regrows. Spread small pieces under mesh or let them float, and they multiply rapidly into new mats. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Riccia fluitans is mildly toxic to pets. Crystalwort (Riccia fluitans) is not individually listed by the ASPCA, and the genus Riccia has no established ASPCA classification; treat it with caution and verify with a vet rather than assuming it is safe for pets that may eat aquarium plants. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Riccia fluitans deep-dive guides

Every aspect of riccia fluitans care, each with its own calibrated guide:

• Riccia fluitans watering schedule
• Riccia fluitans light requirements
• Best soil mix for riccia fluitans
• Riccia fluitans fertilizing guide
• When to repot riccia fluitans
• How to propagate riccia fluitans
• Riccia fluitans growth rate & size
• Riccia fluitans cold hardiness
• Riccia fluitans temperature & humidity
• Is riccia fluitans toxic to cats & dogs?
• Is riccia fluitans toxic to cats?
• Is riccia fluitans toxic to dogs?

Featured in these plant shortlists

Riccia fluitans qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best plants for a north-facing window — Houseplants for a north-facing window: bright, even, indirect light and no scorching direct sun. Each pick verified against its documented light needs.
• Best fast-growing houseplants — Houseplants documented as fast or vigorous growers — quick to fill a pot, cover a pole or trail down a shelf.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Riccia fluitans is also commonly called crystalwort or floating liverwort.

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