They sould start showing signs around 6-8 weeks (slight colouring in the unpaired fins of the males) if fed well on livefoods and regular waterchanges. Breedable around 4-6 months. I have bred the Cap Esterias GBL 85/6 strain many moons ago and I got a great deal of males with a higher temperature so keep the temp down a little. 72'F and you shold get a more balanced sex ratio.
Regards
BigC