Using ink to better enhance the shape of urogenital papillae and presence of urogenital pores to determine sex. Eventually with a lot of practice, ink should not be necessary and the fish handler should be able to determine sex quickly enough to separate males from females without killing or injuring them. It is advantageous to raise only males because they grow faster than females which stop eating when they are mouth-brooding eggs and later fry. With no reproduction in the pond, grow-out fish do not have to compete with fry and fingerlings for food and thus grow larger.