When I started out, I did much the same as you. Started out with a small tank and upgraded to a 37 tall. The plan was to save the smaller aquarium for a hospital tank, so I removed the fish and dumped all the water and substrate into the larger tank. Moved my filter over and ran it in tandem with the new filter that I had bought. I too had hoped I wouldn't have to do more than a mini cycle, but fact was, the bacteria in the small tank was just not enough to do much in the 37 gal. It did however give me a head start in that I immedately had an nitrite and nitrate reading. I dosed with Safestart and my nitrites went away within just a few hours, but I still had to do PWCs until my ammonia reading went away.
What all did you move into the larger tank? It could be that the bacteria that processes the nitrites has survived the move and is working a bit faster then the bacteria that processes the ammonia. If that is the case- with just the five danios in your tank, your ammonia levels should fall off fairly quickly.