I did exactly that, transfer my bacteria. It did help, but adding feeder fish was a game changer.Eheims classics are the best. If you already have the RRS in the 25g all you need to do is take all the filtration from that tank as well as all the water and place them into the 55. You dont need to do any messing around with bottled ammonia or extra BB.
That's what I heard about Ehiems, that they are solid. That being said about Ehiem, I am already having problems with it. If you see this picture below,
That latch cracked right through the middle on the first day of install. Now just tugging on the green tube, the connection un-clips. You can imagine what happens next. Water pumps out of control from the filter pushing water. I have contacted Ehiem about this problem. It should still be under the 30days, so hopefully they can cover that under the warranty.