This plant is a variant of Ludwigia inclinata var. verticillata, with spiralling submerged leaves growing very densely. It is probably a mutant of L. inclinata var. verticillata ‘Cuba’ that was found in a Vietnamese aquatic plant nursery.
This variant is a little easier to grow and develops better coloration. It needs very good light to develop its beautiful red shades, just like CO2 addition and soft water are vital to ensure optimal growth.