Threadfin Rainbowfish (Adults and Fry)

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.

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.

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.

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.