Blaberus fusca breed well and get larger than dubia and are also very narrow compared to other blaberus species. Some refer to them as the dwarf cave roach although they actually have a longer body than the Blaberus giganteus, but shorter wings. You will need considerably more than a pair to get a colony going, how many varies upon your needs but waiting 6 months to have a self sustaining colony is interminable.