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Threadfin Rainbowfish (Adults and Fry)

September 8th, 2008

In a 20L aquarium, I have a small colony of Threadfin Rainbowfish, Iriatherina werneri, that I’m attempting to breed. These blue-eyes are beautiful fish that I’m hoping to eventually have a huge school for my 75G aquarium. The males are especially brilliant, displaying long fins, which they use constantly to prove their dominance to other males, and to impress females.

Threadfin Rainbowfish

The males also tend to get a striking headlamp, a bright yellow/orange stripe along the top of their head, when they’re courting females. The females are not pictures here, but they do not have the elongated fins that the males do. It’s quite easy to tell them apart due to the noticable difference in finage.

Threadfin Rainbowfish

As you can see from the backgrounds in these pictures, I’ve been using spawning mops made from acrylic yarn to try and harvest eggs. The goal is to float these mops, have the fish lay eggs, and then remove the mop and place it into a hatching/rearing tank. By cycling two mops between these tank every 10-14 days, I hope to constantly have new fry. So far, I’ve been successful, but only on a very small scale.

Threadfin Rainbowfish Fry

The fry are absolutely tiny when they first hatch; no more than a millimeter or two long. Right now, I have a couple that are 5-6mm long, but recently lost some to a Hydra infestation. I feed the newly hatched fry GP 5micron powder, which besides green water is just about the only thing that will fit in their tiny mouths. I’ve started feeding the larger fry some baby brine shrimp. Hopefully, they’ll grow up fast, and will be able to go in with the adults soon. If anyone’s successfully bred and raised these fish, I’d love to hear some advise.

13 Responses to “Threadfin Rainbowfish (Adults and Fry)”

  1. Phillip Brown Says:

    These are new to me, what a striking fish. Well done in breeding them.

  2. lolly Says:

    oh that acrylic yarn finally has a noble use!
    great photos 😉

  3. Kim Says:

    They are beautiful and I’ve never seen or heard of them before. Do they eat their fry?

  4. guitarfish Says:

    They’re great little fish. The fry are tiny, so the adults will eat them, although I’ve heard of some folks having success breeding them with the adults when the tank is crammed with java moss. I don’t have enough moss to fill a 20G tank though, so I’m separating them out.

  5. 75G - Cleaned Up-- Guitarfish Says:

    […] replaced them with about 60 Threadfin Rainbowfish (Iriatherina werneri) that I had kept in quarantine for the last few weeks. I also intend to fish out […]

  6. 75G - 2 Weeks In-- Guitarfish Says:

    […] tank is also packed with about 50-70 Iriatherina werneri (Threadfin rainbowfish), and a few other Melanotaenia praecox (Dwarf Neon rainbowfish) that I had from another tank. While […]

  7. Rohan Says:

    I have managed to breed Threadfins in a 1 foot tank at 21.5 degrees and a pH of around 7.5-8.0. Although I was trying to breed from the pair, I was unaware that they layed eggs until I saw a few babies at the surface, and they were absolutely tiny, I struggled to see them at times.

  8. Mike Says:

    Gorgeous rainbows! Seeing the Appistos you work with and the F1 angels I’m wondering if you do anything to your water. If so what are the parameters these rainbows kept in?

  9. Loddeur Says:

    I was also wondering what parameters these fish need. I seem to find contrary information.

  10. Jordan Says:

    A little while ago I moved all of my fish (swordtails, tetra, and 1 male and 1 female blue rainbows into another tank, i left the other one still with the water in, and gravel standing for about two weeks. A couple of days ago I sold it and so started to empty it, when i noticed the jug of water had some life in it! I assumed it couldnt have been a fish as the tank had been empty wioth no filter etc, but i think it may be a rainbowfish fry looking at this picture-it looks identical! i’m slightly puzzled, but have put it into a jug of water (changing the water with my current tank water everyday) until i can get hold of a 20L aquarium to keep it in, and feeding it liquid fry food. Any advice?

  11. guitarfish Says:

    Jordan, thanks for your comment! It’s always fun to find surprise fry in your tanks! It sounds like you’re doing everything you need to do feeding and caring for them. The smaller the fish you can get to them, the more success you’ll likely have. Good luck!

  12. Grissom Says:

    I have a species tank of rainbowfish. I am currently raising 37 fry in a 4ft tank while my adults are in a 1ft tank with some Java moss. I found that the adults do not bother to eat the fry. When the fry got to about 6 months I found that they started spawning – not a lot of new fry but its a start

  13. guitarfish Says:

    Grissom, this is very exciting! I love finding fry in my tanks, and it’s even better when they can be raised up with the adults.

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