This light green lawn-forming Helanthium (Chain sword) is great for aquascaping. It is also sold under the names Echinodorus tenellus, E. tenellus “Green” and Helanthium tenellum “Broad Leaf”.
The plantlets are best planted into the substrate individually at a small distance. Under strong light (ideally 0.5 watts/litre or more) and a good nutrient and CO2 supply the plant will readily reproduce by forming long runners with many plantlets. Should it grow too fast, just cut off the new runners. If the lawn has grown too dense you ought to thin it from time to time.