not sure on diet, but i do remember an article on PFK a few months ago about how what are called hong kong plecs arent actually that at all but some hillstream species that isnt a plec. id need to dig up the article to tell u exactly what they are.
Honk Kong Plecs are actually Hillstream Loaches, they need temperate tanks with lots of flow and high oxygen levels. Visit Loaches online and you will find some of the most knowledgeable people where Hillstream Loaches are concerned