Rotala sp. 'Nanjenshan' is native to Taiwan and is likely a natural hybrid between R. rotundifolia and R. wallichii.
 
It is firmly established in the aquarium hobby and available through both retail and trade, where it is sometimes mistakenly labeled as Rotala 'nanjean' or Rotala 'najean'. 

Like the more difficult R. wallichii, Rotala sp. Nanjenshan grows far more easily in water that is soft and rich in carbon dioxide.
 
Unimpeded light and lots of iron are important as well and contribute to a rich reddish color in the apex of the stem.
 
Finally, a well-designed and steady fertilization routine is important; without one, stunting and blackening may result.
 
It does have its needs, but isn't exceptionally hard to grow. 
The growing tips of this plant naturally arch downward and therefore lend it well to aquascaping.
 
A large grouping planted behind some Cryptocoryne or hardscape makes an effective focal point.
 
To achieve a more compact appearance, give the stand a haircut and wait for the abundant side shoots to grow in.