I originally got a pair of gerbils (Now around 14 weeks old) from a school biology teacher. They have babies every 5 weeks, so I figured Id take a pair to at least help with overpopulation. (I eventually sexed all of the gerbils and put the males and females in separate tanks). Anyways, the mother had another litter (Now around 6 weeks old) I recently upgraded to a 20 gallon Long, and was wondering how difficult it would be to introduce another pair of young gerbils to my current pair. I currently have a 14 week old pair of females, and planned on getting more females. How difficult will it be to introduce them?