The primary function of the caudal fin (or tail fin) in Tilapia, like in most fishes, is to propel the fish forward through the water and to assist in steering and maneuvering. The caudal fin acts as the main engine, pushing water backward to generate forward thrust. 

Tilapia, like most fish, primarily uses its pectoral fins for steering and changing direction, along with its caudal (tail) fin for propulsion. It uses its pectoral and pelvic fins, along with its dorsal fin, for balancing and stability while swimming.