Given gerbils are from Mongolia that would be a heck of a trip to get dinner
BP love gerbils however they are more aggressive than your regular rat or mouse, more expensive and very hard to switch back from once a BP imprint on them (therefore not something sustainable or advisable)
If a BP was eating a certain prey it will again but people lacking patience prefer offering another prey type even though it's not a good solution but rather something setting you up for complication in the future.
Again PATIENCE is the key.
I have NEVER had any issue getting an animal back on food they always do sooner or late maybe not as fast as YOU might want them too but they do.