First rat ever!

Are you worried your Bp will ingest some aspen? It should be fine.

My corn is on aspen, and one of my bps is on reptibark and I've had no issues with them even getting substrate on the mouse.

My first Bp was fed in a separate enclosure before I got him. I continued to feed him in another tub till I found this site. He now happily eats in his enclosure and I've seen no change in his temperament.

Congrats. I transitioned two of my 3 month old baby balls to rat pups yesterday with no problem. If anything, the feeding response was even more aggressive than with mice, so that looks like a good sign.