It may not be clear to a new snake owner that the biggest reason for not feeding in the living quarters tank is to avoid aspen chips or other substrate particles from being accidentally ingested along with food. These chips or particles can lead to gut impaction [or irritation at the very least], which is a dangerous condition [see my post about this nearby under "Impacted?"]. Corns will drag their food around sometimes, so having any chips where they are fed can lead to them getting stuck to feeder mice.
For feeding, I use a breadbox sized Rubbermaid container with holes drilled in the top for air. I put the mice in a small plastic cup laying sideways on top of plain white [no chemicals or dyes] paper towel over the floor of this container.
No chip on the [mouse] shoulder,
Doctor Mike