It is case-by-case basis depending on the duckling. I have both small and larger Tupperware for different situations. If the duckling is lethargic I use a smaller one to both keep them in place and keep the cord clean. If the duckling is energetic, but unable to stabilize or stand I use a larger one because that fighting to stand is going to build those muscles and they need room for that. I have had ducklings where I start them off in a smaller Tupperware container in the brooder because they just are not actively trying to be mobile. Then I dose them with poultry cell, leave them in the smaller one overnight and the next morning they really spring to life so I graduate them to a larger Tupperware container with room to move. On the other hand I have had ducklings where I go to move them to the brooder and they are energetic from the start, but still have cord to dry up and aren’t able to stabilize themselves. For those I skip the small Tupperware and put them in the larger one right away because they need to practice learning how to walk.