you will end up having to feed him/her rats when its a adult so as soon as you make the change the better, cos as you have probaly heard that they are notoriusly fussy eaters...
here is a guide if your curious about nutritional values...
Ella is now takin rat pups which is gd! shes 5 months old and last weighed she was 110g so when do u think move her on to the next size and wud it be rat fuzzy?
I have one at about 120g that I'm going to move onto Rat Fluffs as soon as I can get some. A lot of places go from pups to weaners which is too big a jump imo.