Christmas moss (Vesicularia montagnei) is a popular aquatic plant in the aquarium hobby. It is a type of moss that is native to Southeast Asia and is commonly found in freshwater rivers and streams. Christmas moss gets its name from its distinctive shape, which resembles a tiny Christmas tree. 

The plant is relatively easy to care for and is commonly used in aquascaping to create natural-looking underwater landscapes. It grows slowly and can be attached to driftwood or rocks to create a natural-looking effect. 

In addition to its aesthetic value, Christmas moss also provides a range of benefits to aquarium ecosystems. It helps to oxygenate the water, absorb nutrients, and provide a habitat for beneficial bacteria and small aquatic animals. Overall, Christmas moss is a popular and attractive addition to any freshwater aquarium.