Whatever livebearer species it may concern, I breed them on quality terms. Those that won't meet up the characteristics or traits of their own kind sufficiently will be culled. The culled ones will be put in one of the mutt tanks, or put seperate for those who are in favor of them or if a store is asking for these types of livebeares of a lesser quality.
If you're a serious breeder of a certain kind of livebearer, culling is in place each generation of those fish. Doesn't mean that they're unhealthy or ugly fish. But if a deformation or mutation is at hand and that would be passed on dominantly in future offspring, that's something you don't want as a serious breeder. So, such fish should be culled from the rest. They won't be killed, btw. Some do that but I won't. There's always an option that they'll get another home.
I hope they take after the father
I did hear about this before I remmeber, but whenever I hear 'culling' I instantly think about euthanasia or something like that... 
