sexing cacatuoides

[Eva32181]

My cacatuoides are doing well, but I'm having trouble telling the girls from the boys here. A few of them are clearly males, very large and colorful, and one is definitely a female - she's bright yellow and guarding fry. But there are others in the group that are not as big as the big males, but don't really look like females either. I understand females only turn yellow when ready to spawn, right? Any ideas on distinguishing them?

 

[Neil]

Eva,
With line-bred aquarium strain fish, like the cacatuoides that you have, there is some difficulty in sexing. Usually an easily sexed fish, these fish have been produced via the selection of optimumly colored females as the broodstock focal point. Simply put, the females that carry the most red w/black reticulated markings on the unpaired fins, almost to the point of resembling a male. In turn, they produce fry that are similarly colored and can be quite difficult to sex until they become adults.
However, there are a few things to look at. The ventral fin of the female usually has a black anterior edging, the red/black markings are usually lighter in the female and the females "base" color is a little lighter with, perhaps darker black markings on the body.
Of course, the easiest way is when the female goes into her yellow breeding coloration. Hope this helps.
Neil