going from mice to rats

i want to change rush over to rats. is there anything special i should do to change him over? he eats f/t.

You could always just offer him the rat, he may take it no problem. If he doesn't seem interested in the rat, thaw out a mouse and rub it all over the rat "scenting" it. This is what got my female to take her first f/t rat. After scenting it once, I never had to again, she switched over pretty easily.

None of mine have ever had issues taking a rat, I'd start with rat pups first and work up to larger ones to be sure they take it.