Vallisneria are perfect for you Tang. tank. I have a mix of Italian and Corkscrew Val. They, IMHO, are a good mix. Also, there are actually Vallisneria species growing in the lake, but I don't know which species. That means, you can recreat (somewhat) the environment theat would normally occur. P.S. I'm glad to see another interested in Lake Tang.
P.S. I would check out The Krib. The first memo suggests that V. aethiopica is the native plant in question.