What exactly do you mean by 2 generations. You get pinheads and those grow up and breed to get more pinheads? If so I'd like to know your technique because I have never had mine get over a 1/4" if that and it takes forever for them to get that big. I know temps play a huge factor in growth rate and I've mostly been keeping them too low but I have a new cabinet now that stays at 88 so I might try it again.