Riccia fluitans

Overview

Riccia fluitans (crystalwort) is a bright-green liverwort famous for pearling — under strong light and CO2 its fine, forked branches coat themselves in glittering oxygen bubbles. Naturally a floating plant, it was made iconic by Takashi Amano, who tied it over stones to grow it as a luminous carpet. It has no roots and never truly attaches, so it takes a little more management than a rooted plant, which puts it in intermediate territory.

Planting & placement

Riccia is not planted in substrate — it has no roots. To grow it as a carpet, sandwich a thin layer over rock and pin it under fine mesh or a hairnet so it can’t float off, as our how to plant aquarium plants guide describes. Left loose it makes excellent surface cover for fry and betta tanks. For carpeting technique, see our how to grow a carpet in a planted tank guide.

Light, CO2 & ferts

Riccia is a high-tech plant when grown as a carpet. Give it medium to high light to trigger dense growth and pearling, and inject CO2 to keep the mat compact and low — see our best light for a planted tank guide. A full liquid water-column fertilizer feeds its fast growth. Without strong light and CO2 it grows loose and buoyant rather than carpet-flat.

Propagation & problems

Riccia propagates by division — it simply splits and multiplies, and any fragment grows into more. Trim the carpet frequently to keep it thin and stop lower layers from browning, detaching and floating up; save trimmings to start new patches. The main problems are floating away (pin and trim) and a rotting, buoyant base from an overgrown mat. Floating Riccia is far lower-effort and doubles as valuable cover and grazing for shrimp and fry, so many keepers use it that way instead of fighting the carpet. Whichever route you take, keep flow moving through it to prevent debris settling. It is more work than a rooted carpet, but few plants match the sparkling, oxygen-beaded look of well-kept Riccia under strong light.