Female Peacocks reach sexual maturity at about ~2.5".
If you only have one pair, once they do spawn, the male may make a sole females life pretty miserable! He'll continue to chase her even though she's holding. If you can, pick up another 1 or 2 females. Maturnal mouthbrooders like the auloncara do best with about a 1 to 4 male female ratio. 1 to 3 can work as well in a community tank.
Typically, when I'm starting a new colony, I get 10 individuals and auction off the spare males.
Good luck with them!