South American moss

South American moss is an aquatic moss of the genus Vesicularia (Hypnaceae) not identified to species. Despite the name, nothing links it to South America; the name is usually explained as evoking the rainforest. Some sources suggest a South-East Asian origin, but its provenance is unclear. Although called a willow moss, it is regarded as a different moss from what is usually sold as willow moss. The branching gives it away: willow moss tangles irregularly, while this moss branches like a feather into triangles (deltas) that build up in layers. It is brighter green and fuller than willow moss, and grows more slowly. It grows in low light and CO2 is optional, though a little CO2 helps the triangles form neatly; under strong light a shaded spot suits it. It attaches only weakly on its own, so fix it with fishing line or glue. The more it is trimmed, the denser it grows. It is a widely available staple moss at specialist shops in Japan.

High temperature, hard water or high dissolved solids reportedly turn it brown, so keep it below 30°C.

Grows without CO2 or fertiliser; a little CO2 improves its shape