Complex sentence: The largest characin is "Hydrocynus goliath" at, while the smallest size is about in the Bolivian pygmy blue characin, "Xenurobrycon polyancistrus".
Split into simpler sentences: The largest characin is "Hydrocynus goliath" and, both of which are. The smallest size is about in the Bolivian pygmy blue characin, "Xenurobrycon polyancistrus".