Hydrocotyle sp."Japan" is the popular name of the plant in different plant forums. It is a variant of Hydrocotyle tripartita from South-East Asia.

It is characterised by fast, compact growth and small, intense green leaves on vertical stems. The plant is carpet-forming (5-10 cm tall) and its compact growth can be promoted by physically pressing the carpet with your hand when maintaining your aquarium. Carpet formation and compact growth do best in good light.