What I am calling Crypt. crispatula var. flaccidifolia (left) vs Crypt. crispatula var. balansae 'red stem' (right). Ive grown the flaccidifolia for over 10 years thiking it was a limp variety of balansae. Some people also grow a similar looking palnt and call it C. retrospiralis but based on the description for C. retrospiralis on the Crypts pages I think this is incorrect. The characters that distinguish it are the limper leaves (more flaccid!) and the undulating margins of the leaves compared to the balansae that usually has a straight margin and bullate blade.
There are a number of varieties of Crypt. crispatula var. balanasae in Australia - this one is the 'red stem' variety where the petioles and central vein can be quite a dark red. There are others with creamy white petioles and veins that I unimaginatively call Crypt. crispatula var. balanasae 'green' to distinguish it.