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How to sex Swordtails

Discussion in 'Fish and Aquarium - all types' started by Boo Boo Magoo, Jun 13, 2006.

  1. Boo Boo Magoo

    Boo Boo Magoo New Member


    Could anyone tell me how old will my swordtails have to be before I know what sex they are?

  2. t_chelle16

    t_chelle16 New Member

    I've never actually bred swordtails before so I don't know for sure. But I would think that that after a few weeks, their fins would start to develop enough that you could make out the sword on the males.

  3. Boo Boo Magoo

    Boo Boo Magoo New Member

    Thanks chelle, they are 7 weeks old now and none of them show any signs of growing a sword as yet. May be they are just all females at the mo and will only change when they are away from the adult male in my tank.
  4. kc5gvn

    kc5gvn New Member

    Males have a rod-shaped anal fin (gonopodium). Females have a fan shaped anal fin.
  5. rgg

    rgg New Member

    I was able to distinguish mine in close to around 4 months. Had these exotic top quality koi swords.

  6. Boo Boo Magoo

    Boo Boo Magoo New Member

    Wow 4 months! Thats another 8 weeks! I've already got another 6 babies in a breeding net and the adult female is pregnant again. I'm gona be over ridden with these little orange critters (mine being your common garden variety). Thanks for the info though Raghu. It looks like I may have to send them to the shop early as I've only got a small set up and I'll never know what sex they are.
  7. Boo Boo Magoo

    Boo Boo Magoo New Member

    Today I notice that 3 of my 7 adolescent swordtails have grown gonopodiums. They are now 10 weeks old, so that answers my question really. Does anyone know when the males become aggressive towards each other?

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