I had a kuhli loach that lived under a UGF for over a year--he's still alive and fine. My kuhlis bury themselves under logs, plants, large rock--anywhere they can. Never seen any harm from it, other than a few disturbed plants. My weather loach will dive into the substrate--sends it flying--and never hurts himself.
There are many fish that 'hunt' this way--they cover themselves with the substrate, then wait for dinner to swim by. Or, the shuffle along through the substrate with their noses and root out the little crunchies that live there--scuds, snails, etc.