your young girl is a young boy, the gold is the flashing color displayed by the males when competing for spawning rights.
Do you know the collection spot? There are a couple places where they are from that have different coloration. One river has more yellow Threadfins and the other has a more gun metal blue color. if they were LFS bought you may never know which river they are from.I have 6 Threadfin Rainbowfish (Iriatherina werneri) 2 males and 4 females. I just added 2 females yesterday and one is a really young girl, very small. The 2 males have been displaying and one of the males actually mated with one of the females a week or so ago.
Both the original males and the 2 females have gotten brighter in coloration and have been slowly turning a yellowish color. The mating behavior has continued all along.
However, when I brought the 2 new girls home yesterday they were a very pale silver, particularly when compared to the original females.
Today, the new girls even the young one, are turning a yellow honey color. I have searched around on the web and cannot find out anything about this.
All the fish are swimming around active and seem healthy. Everyone ate well and the two males act happy to have more girls around.
Is something wrong or is the golden color when they are more actively breeding?
I just think it is odd that the two new females turned color so quickly-- even the little girl.
I really don't want anything to happen to these fish. I really like them a lot.
Hope someone can help me!