About Riccia fluitans L.
Riccia fluitans, commonly called floating crystalwort, is an aquatic floating liverwort that belongs to the genus Riccia. It is popular among aquarists, where it provides a retreat for young fry and is used in tanks for live-bearing fish. In the wild, it grows floating in ponds, and often forms thick mats on and under the water surface. It typically grows quickly when at the water surface. When kept around two to three inches below a standard fluorescent bulb, or growing in a pond exposed to full sunlight, it will form dense, bright green mats. Any single branch or antler bud can grow into a large colony if the plant is kept in suitable conditions. While it usually floats, it can also attach to underwater objects like logs and rocks, and can be secured in place with plastic mesh. Floating crystalwort is generally not compatible with duckweeds, because duckweeds quickly cover the water surface and crowd out Riccia fluitans. It is also easily overgrown by hair algae. The species epithet fluitans is Latin for floating.
