I use cardboard gaylord boxes ontop of a plastic pallet. I have six boxes, I typically can get 3/4 to 1 ton in each box. I threw one box out since it was starting to get warped and falling apart. I am considering making a woodbox ontop of the pallet. Not sure if anyone had done this before and has any recommendations. I know I want to have one side have a pull out side so it is easier when I get to the bottom of the box.
I dont use wood boxes but i do use pallet bins as well. I can get an endless supply of large (4x4x4)very heavy cardboard boxes complete with tops from work for free. They are used to ship glue pellets and are shipped with 1500 lbs in them. I am sure I have at least 1500 lbs of rice in there if not closer to 2000 with no problem as the amount goes down i cut down the side of the box to make easier access. When they are empty I burn the old one and replace with a new one.
Unless the wood is going to be outside you really don't need the treated. Just make sure you don't get it too sealed on the bottom that water can't escape. I would suggest using a coated deck screw or galvanized.
I am going to keep these bins outside in my "junkie shed." No heat, but gets water in every now and then. I got them from work and we are under new management and they are little less given than the old managment team. I figure go with treated wood, so I would not have to it for a while. I was going to put drain holes on the bottom piece of wood and put cardboard down before I fill it up, I burn with nut coal from UAE.