The topminnow Aplocheilus lineatus detects and localizes the source of water surface waves with its cephalic lateral line system. Previous behavioral experiments with Aplocheilus have been performed with blinded animals. We tested how well sighted Aplocheilus can be trained to discriminate between water surface waves of different frequency and duration and whether the animals used information from the lateral line for discrimination. Our data show that sighted topminnows can be trained to respond to and discriminate between single-frequency water surface waves and that lateral line information is required for the discrimination. Thus, blinding the animals by surgically removing the eyes in many cases is probably not a necessary prerequisite for testing the sensory capabilities of the lateral line in surface-feeding Aplocheilus.