I have three sweet new six-week old chicks that I will be introducing to my existing flock in a couple of months once the little ones are bigger. I have the chicks in a small brooder box for now but need to use something larger to accommodate them for the next couple of months. Any recommendations on how high the walls of the box should be? I would like to use a metal stock tank but the walls are only 2' high. Would that be sufficient or do I need something taller? I plan to cover the top with mesh to prevent anyone flying out. I appreciate any suggestions!