Hypans can be considered omnivores but most lean towards a diet higher in animal proteins.
How many times have you tried feeding veggies? You can't really expect to feed a couple times & have them eat it right off, even herbivorous plecs don't necessarily take veggies their first feedings. They often need to be taught that veggies are food items. Some species of plecs prefer some types of veggies & others won't touch them. It comes down to trial & error in determining waht your fish will eat. There are also a couple of tricks to get them to take veggies - the garlic trick & sticking wafers in the veggies are two often used.