You just got to make sure that the large ones in that colony are adult roaches and not just large roaches if that makes sense. On the roachcolony website he makes says there are 20 adult females and 10 males which is important to keep at least a 2/1 ratio of females to males (preferably 3/1) where on the other site they may just give 50 random adults. I obviously dont know this for sure and i dont want to try to give any websites a bad name, but i do know for sure that the guy from roach colony specializes in roaches, he doesnt handle any other live foods so he knows exactly what hes doing with them. And he is pretty helpful to if you email him with any questions, iv dealt with him a few times.
I want to start a colony but the girlfriend wont let me. So i just buy 200 mediums every 3 weeks and keep them in a small fish tank but thats like £30 a go :s