Reply To: Mysterious fry appear in tank with no adults! Welcome to the website! › Forums › Other Freshwater Fishes › Species Breeding › Mysterious fry appear in tank with no adults! › Reply To: Mysterious fry appear in tank with no adults! October 8, 2007 at 11:09 pm #12520 CrazedpufferParticipant Good luck with the fry. How big do the rainbows have to be to breed? I have a male and a female and would like to give it a shot