Hehe I think I'm going to get a thrid very soon.
I saw a little black bershire eariler in the week at the same pet store I got the others, but I'm unsure since her cage mate seemed to be shivering a bit when I briefly saw her.
The little girls now have a larger tank, so a third would be ok. This time I'll definitely stop at three, though it'll be a tough one. I want a rat room
.