Cleanliness & good water quality is the key to healthy barbels
...although i still reckon corys act more natural in sand than opposed to gravel, you wont see a cory dive into the gravel nose deep and sift through it like my lot do especially the albinos...(very amusing to watch them on sand).
I absolutely agree with you! My cory do some active sand diving too, and it's a great thing to watch. When I first switched from gravel to sand, the change was just amazing. They went from looking like it was work to find food in the gravel, to acting like they were on vacation at a water park!