well im not really sure how long
but i used to go to the aquarium shop n choose those pregnant ones
once i get them, i seperate them n put lots of plants
den some will give birth in a few hours
some in a few days
when its really big n u can see the dark spot
den it should be soon
i used to seperate n put a female per location
but recently, i put all the pregnant females in a bigger place, put lots of plants and it was okay
they dint eat them up or anything
the fries have grown
its big now
but i cannot guarantee the females will not eat them
n once u have ALREADY seperated them n they gave birth, never put the fry with another fish coz they will definitely eat them....