Reply To: IDing rainbowfish (species and gender) Welcome to the website! › Forums › Other Freshwater Fishes › Species Discussion › IDing rainbowfish (species and gender) › Reply To: IDing rainbowfish (species and gender) October 11, 2007 at 2:20 am #12568 L777Participant Atlantis, keep an eye on the *shape* of Aurora as the fish grows over time. As males age, they develop a distinct hump on their back — see crazedpuffer’s male. If Aurora is near adult size for whatever species he is, I’d vote female based on shape.