So I've seen that most everyone here has a wire cage. I know they have advantages like more climbing area and air flow, but I was planning on using a 40 gallon breeder tank. I had an idea to take these things i have laying around from old cages ( they look like the top of this cage http://www.dkimages.com/discover/previews/743/145718.JPG ) and attaching two of them on top of each other and then attaching that to the screen top of the tank. Of course I would cut holes so they could access it and all that. Its hard to explain but hopefully that made sense lol. I figured this would help add space and ventilation. If I did this, and added lots of climbing things and levels within the tank, that it would be adequate to house 2 rats?