Mine started breeding at about 4" for the male, 3" for the female.
I started with about a half dozen, the pair killed off all others.
They hit @ 6-7" by the 3rd spawn, and after that, the male killed the female.
The fry were easy to raise in an algae filled tank, and fed 4 or 5 meals per day of Artemia, until they went on to prepared foods.
By about the size above, the larger ones needed to be separated out, to separate grow out tanks, or they'd eat their smaller bros and sis's.