Heteranthera zosterifolia was commonly known as Stargrass. It originated from South America. It's a very beautiful aquarium plant. Under strong lights, it grows fast and needs frequent trimming to ensure that the lower leaves are still reached by the light. Star grass often throws water roots on the stems. On shoots floating on the water surface, small blue flowers will grow above the waterline.
Sold as a bunched plant with a lead weight. Fresh cut with 4+ stems.
Pictures are not the actual plants you will receive, but a sample representation.