Heres a little observation related to this problem :
I had this one pair of p. harveyi and they had quite a lot of fry swimming around in their tank, so I decided to take out some of the fry into another tank. They were quite big at the time, but before I could determine sex.
After some time it showed up that these were all males, and this was the reason I made this thread, because it really annoyed me that at whole tank now again showed just males 🙂
But then I started taking some of them out again into new tanks (because now I want to experiment a bit) .. and when I thought they were all out … :blink: … I found one small one, much smaller than the others .. and this one I think is female.
And looking at the rest of the big brood – it does seem that after I had taken out the bigger ones, – more of the remaining seems to have a chance of being females. They are still not at all the same size as the first I took out (it could be more than one brood)
But it makes me think that there may be something about this with males being bigger, stronger and maybe ‘out-eating’ the smaller females. And maybe I did a good thing by – for other reasons though – separating some of the bigger fry out at an early stage.
Anyway, its just an observation ..