Barbels

From The Aquarium Wiki

Barbels are the slender, whisker like tactile organ near the mouth. Fish that have barbels include the cat fish, the carp, the goatfish and some species of shark. They house the taste buds of such fish and are used to search for food in murky water.

Fish that have barbels require a rounded substrate to ensure that their barbels are not torn or damaged from contact with sharp gravel.