New rodent friends

My friend Julie's sister bought two female rats for her daughter. After they brought them home BOTH rats had babies so they had over 20 rats. Some of the rats were donated as food but the others they gave to friends as pets. They had a couple of rats left that they needed to find a home for and of course I folded and now I have rats. The boy is very friendly and his name is Tubbers; I had tried to name him Rizzo but he's such a fat little rat that I just kept calling him Tubbers and decided that must be his name. The female is fairly anti-social and I am planning on donating her to the Wildlife Hospital to be a breeder so I named her Preggers. I was hoping they would have babies and I could keep one of the boys to keep Tubbers company. It seems like he would be lonely if he was on his own. Grant really likes them and always comes over when I have them out. Twice he has brought a toy over to them; poor Grant doesn't understand that the rats can't play with him. At first I had put them in a 10 gallon tank that I had in the attic but they looked so crowded in there that I ended up making a trip to the pet store and bought them a nice big cage. They seem happy now and come to the cage door whenever I open it so that they can get their treats.