when they are babies it is hard to tell but males tend to be larger then the females... so if you want a male try to pic the largest healthy one in the batch The Green Terror is a very colorful deep bodied fish marked with various striping on its body and face. The male has a green and blue metallic sheen, a blue anal fin, and a red band at the edge of its tail fin. Mature males will develop a hump on their heads. The female is a darker tone with a green anal fin, and are a little smaller than the male. The Green Terror will live over 10 years if well cared for. Hope this helps ...and good luck ...post up pic when you can..