12"x12"x30" should be fine for individuals or even pairs. i keep up to 4 adults in a 23"x16"x16" cage with branches, vines and a few hides and they do fine. you might choose the larger size if you want to keep 3-4 adults together rather than pairs. having the cages on the floor should be fine as long as they aren't next to any air vents that would blow cold or hot air into the cages.