The water sprite will repoduce on its own. It forms new plantlets on the margins of older and dying leaves. I prefer to float my water sprite, although it can also be planted. It should grow great if you float it, have relatively warm water (75+F) and plenty of nitrogen. H. difformis (wisteria), as as jgc mentioned, is a great plant also, but I would suggest using it in planted form. It will reproduce by side shoots, or you can also replant clippings. If you put a clump of java moss in the tank, make sure you spread it out, as lower sections are proned to die if they do not receive enough circulation.
Eheim Pimp #181
29g High-tech jungle
5.5g Low-tech jungle
2.5g x 2 Low-tech shrimp and moss