The fish of the genus Petrotilapia, contain the largest mbuna in Lake Malawi. The fish have mainly tricuspid teeth, that they use to comb through the aufwuchs, pulling off diatomous algae, microorganisms, and loose particles. Plankton is also eaten by Petrotilapia. Territorial males will protect are area that varies between 7 to 20 meters squared against conspecifics, though heterospecifics are mostly ignored.
Males of the sp. "Yellow Ventral" vary from having blue on the top flank, with yellow on the rest of the body, to being completely yellow. Females are typically grey/silver/yellow to brown, with a checkerboard like pattern on their body.