What No One Tells You About Fish Gender Male and female fish often look different. In swordtails, only the male has a long, thin extension on the tail. Males are usually more colorful than females. People used to think they were different species because of this. Follow for more insightful tips on how to easily distinguish between male and female fish in your aquarium. #FishGenderIdentification #AquariumHobby #DrTimsAquatics | DrTims Aquatics