I'm going to be purchasing six hens this spring! Super excited! Have some questions that I am getting mixed review answers on! First, how often is grit needed? I have a ton of sea shells and have heard i can crush them super fine and give them to the hens?! If i have six hens i need six nesting boxes right?! My husband seems to think that three will be fine and they can share. I don't agree but don't really know! He's building the coop and is looking top keep it simple! Help!!