Im going to start building a cage system for my cresteds and I can't decide what size to make the cages for singles. I have a single male in a 12"x12"x30" cage right now and it seems fine. Is that big enough or would 18"x18"x30" make that much of a difference in size. I know that bigger is better but I'm working with limited space and I want a lot of cages. Also what size would you do for a pair. Would it be ok to have some cages directly on the floor.