feeding problem

ok well my bp is just over 2yrs and this whole problem is my fault ,,last aug i just couldn't get any rats here to feed him and he wouldn't eat mice any more so after about a month i fed him a gerbil ya dumb i know. so now he refuses to eat any thing but gerbils. i am sure he is hungry man he hasn't eaten for over 3 months. he isn't losing much weight still seems to be good weight he wasaround 1250 grams yesterday ,i really want him back on rats as if we move from here looking way down the road 8-9 yrs ,will have to order feed for him and rather fix problem now so i am being stubron not giving in but ? is how long to hold out .he is great and won't put his health at risk,

Try putting the rat in the gerbil bedding so that it smells like a gerbil.

i have tried rubbing the gerbil all over the rat ..tried getting the mmm blood all over the rat nothing seems to work. i took him out of his tub he was moving around head up tongue flicking got to the rat and soon as he got close he just turned away