sexing young a. nijjensi

[anewbie]

I have a set of f1 nijjensi somewhere between 6 and 10 months old. the largest 2 or 3 are 1 1/4 to 1 1/2 inch and the smallest are around 1/4 to 1/2 inch (big divergence). I only have 9 and want a new pair from the group but am having a difficult time sexing them because they keep morphing their markings. I take black face, black petral fin and tail spot as indication leaning to female other-wise male. I can say that this little fellow who i think is a male was displaying the tail spot and black petral fin earlier today and now he (or she) isn't but still has a slight tail spot (even with flash it is quite dark - they are not shy but never sit still). I'm pretty sure it is a male unless maybe it is a female. This is the largest by a wide margin.

So my question around markings is can a male look like a female anytime he wants or is this just a youthful thing they will grow out of.

 

[KenL]

I’d say that is a male.
I bred nijsseni in the 90s and raised about a dozen fry. The female ones had bigger spots on their sides when young.

 

[Mike Wise]

So my question around markings is can a male look like a female anytime he wants or is this just a youthful thing they will grow out of.

I guess the answer is yes and no. Think sneaker male. At the size you list - especially the smaller specimens - they can look like either sex. I personally wait until I see a dominant female who doesn't change and the same for males.