Fertilising guide
How to fertilise Riccia fluitans (Riccia fluitans)— schedule & NPK
Also called crystalwort, floating liverwort.
More about riccia fluitans
About Riccia fluitans
Riccia fluitans · also called crystalwort, floating liverwort · tropical
Riccia fluitans, crystalwort, is a rootless aquatic liverwort that naturally floats as a bright green tangled mat. Famously pinned down with mesh in aquascaping, it forms a dazzling pearling carpet under strong light and CO2. Vivid but demanding, it sheds oxygen bubbles when thriving and needs high light, injected CO2 and frequent trimming to stay anchored.
Growth habit: Rootless, fast-growing and buoyant; branching forked fronds form a tangled mat that floats unless physically pinned down.
Watch for — 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.
What fertiliser riccia fluitans actually wants — and why
Riccia fluitans is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for riccia fluitans: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed riccia fluitans, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For riccia fluitans:
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. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when riccia fluitans is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for riccia fluitans
Half strength is the safe default for riccia fluitans — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water riccia fluitans first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the riccia fluitans watering schedule.
Signs you are over-feeding riccia fluitans
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for riccia fluitans:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding riccia fluitans
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full riccia fluitans care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of riccia fluitans with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for riccia fluitans
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising riccia fluitans — frequently asked questions
What fertiliser does riccia fluitans need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Riccia fluitans is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed riccia fluitans?
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. 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. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for riccia fluitans?
Half strength is the safe default for riccia fluitans — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding riccia fluitans look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding riccia fluitans year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of riccia fluitans?
Flush the pot of riccia fluitans with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Riccia fluitans care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water riccia fluitans — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise monstera
- How to fertilise pothos
- How to fertilise fiddle leaf fig
- All 5561 fertilising guides in the Growli library