Riccia fluitans

Quick facts

Max height

5 cm

Growth rate

fast

Difficulty

intermediate

Placement

floating, foreground

Propagation

fragmentation

Water parameters

Temperature

18–28°C

pH

6.0 to 7.5

Hardness

0 to 15 dGH

Cold water

tolerated (unheated setups)

Light and nutrients

Lighting

high

CO2

not required, but boosts growth and color

Substrate

floating

Feeding

feeds from the water column (use liquid fertilizer)

Substrate

What this plant roots into (or attaches to). The substrate affects both plant nutrition and water chemistry; see each linked page for full effects.

This plant feeds primarily from the water column, so substrate choice matters more for its fish-tank compatibility than for plant nutrition.

With fish

Plant-eating fish

safe with plant-eating fish (tough leaves or unpalatable)

Diggers (corydoras, loaches)

fine - root system or attachment style handles it

Root-disturbing fish

tolerates fish that disturb roots

Habitat

Distributed across tropical and temperate regions worldwide. The species (Riccia fluitans, commonly called crystalwort) is a liverwort that naturally floats on the water surface in ponds, ditches, and slow streams. The plant consists of branching, flat, bright green thalli (frond-like structures) that form tangled floating mats. Riccia gained fame in the aquascaping world through Takashi Amano's Nature Aquarium books, where he popularized the technique of tying Riccia to flat stones with hairnets or mesh, creating submerged 'Riccia stones' that pearl (produce visible oxygen bubbles) under high light, creating a sparkling, jewel-like effect. This pearling is one of the most visually spectacular phenomena in planted tanks. Riccia fluitans has been known to science since the 1700s as a common liverwort but only entered mainstream aquascaping through Amano's influence in the 1990s and 2000s. The pearling effect occurs because the thin thalli have a very high rate of photosynthetic oxygen production relative to their mass, and the water becomes locally supersaturated with dissolved oxygen, causing visible bubble formation on every surface.

Care notes

Naturally a floater, but most aquascapers grow it submerged by tying it to flat stones or mesh with hairnets, fishing line, or stainless steel mesh. Under high light with CO2, submerged Riccia grows rapidly and produces vigorous oxygen bubbles (pearling) during the photoperiod. The pearling effect is the primary reason keepers grow it; the tiny gas bubbles covering the bright green thalli sparkle under light. Maintaining Riccia submerged is high-maintenance: the plant is positively buoyant and constantly tries to float away. The inner portions of dense Riccia mats die and decompose, releasing the outer portions. Regular retying (every 2-4 weeks) is necessary. Without high light and CO2, submerged Riccia grows slowly and doesn't pearl impressively. As a floater, Riccia is easy and needs no special care: any light, any water chemistry, temperature 15–30°C. The floating form is useful for nutrient export and fry cover but not as visually dramatic. For the iconic pearling Riccia stones, expect: high light, CO2, weekly maintenance, and patience. Available from aquatic plant retailers and hobbyist trades.

Further reading

• How to cycle a fish tank
• Water chemistry for fishkeepers: pH, GH, KH, and what they mean