Re: brooder size: go as big as you can possibly go, unless you already have a bigger and better plan B available for them to move up to. That plan B could be a tractor (that's what I've used for the past 2 years) or a coop for your first flock, or a part of your coop sectioned off if you already have a flock. The more brooder space you have available, the more option those chicks have to choose their own heat comfort zone. They will also spend more time in the cooler end, therefore, they'll feather out faster and wean from the heat faster. And, they'll have much more room to run around, spread their wings, and do their little chick activities.