My normal rescue is a mouser. He had only ever been fed on live (and the crappy skinny Petco live ones at that), and the previous owner didn't feed him often enough.. After three years of living with the former owner he was still only 500 g when I got him. Since getting him in May he has put on over 200 g and is eating rather well. I was able to transition him to frozen thawed, however he absolutely refuses both live and frozen rats. He will turn his nose up and refuse rats, but as soon as I remove the rat and put in a mouse, he is on it like stink on doodoo.
Since he is a male, I suppose I should be able to keep him on mice the rest of his life if I have to right? The FT mice he is eating or about 30 g, and this week I'm going to try and get two of them in him. When he was on life, sometimes he would eat one sometimes two mice. The pain for me was keeping a tank ready to keep the mice alive, watered, fed and exercised if he refused the 2nd mouse.