I always go first to Kasselman for plant info (in a book) because she is a botanist and the book is estensive, but just out of curiosity I checked Hiscock's
Encyclopedia of Aquarium Plants which is more basic and fewer listings and this species is listed. Hiscock has this to say about it:
Blyxa japonica is similar to B. echinosperma, but much shorter and harder to care for. In nature the leaves may grow fairly tall, but in aquarium conditions they rarely reach more than 2-3.2 in (5-8 cm). Even in the best conditions this plant may have a limited life span in the aquarium. For optimum care, provide very bright lighting and a soft water environment.