Glossostigma

Glossostigma elatinoides is a tiny aquatic plant in the family Phrymaceae, native to eastern Australia where it colonizes wetlands and shallow watercourses as an amphibious herb. One of the world's smallest aquatic plants, its oval leaves measure only a few millimeters. In the aquarium hobby it is prized as the quintessential foreground carpeting plant: under high light and pressurized CO2 injection (1–2 bubbles per second), dense mats of bright green creep horizontally across the substrate to form a flawless living carpet. Insufficient light causes upward growth rather than horizontal spreading, so strong illumination is non-negotiable. Thrives in nutrient-rich aquasoil; root-tab fertilizers further enhance density. Once established, it serves as the foundation for world-class Nature Aquarium layouts.

Source: Wikipedia (CC BY-SA 4.0)

CO2 injection required + liquid fert + substrate fert