Crystalwort

The look that made Riccia fluitans famous in aquascaping — a dense floating mat of bright green, branching fronds that catches the light — is also its maintenance challenge. It grows fast, clogs filters when it multiplies, and must be removed in handfuls every week in a well-lit tank. People either keep it permanently or remove it entirely within a few months; there is rarely a middle ground.

In nature it floats freely worldwide in still and slow-moving waters, forming tangled masses. It has no roots or stems in the usual sense — each frond is a single, forked thallus that branches repeatedly and stays buoyant using air pockets within the tissue.

It is sometimes used as a spawning medium for egg-scattering fish species. In the aquarium it grows at temperatures from 20 to 27 °C and pH 5 to 7.5, and does well under moderate to strong light. CO₂ injection produces notably denser, brighter growth but is not required.

A tied-down Riccia carpet is technically possible but difficult to maintain. The plant naturally floats, and keeping it submerged between mesh or fishing line requires frequent trimming as the fronds push upward and break free. Most aquascapers accept it as a floating plant and use it in nano tanks or breeding setups where surface cover is the goal.