Yes, theres wire mesh on top just like with the typical concrete tub rack. There is plenty of air flow as well. The food sits on top of the mesh as do the water bottles (don't have funds just yet for auto watering system). It's actually only 6 feet high, though it looks a lot taller in the pic, so I can reach the top tubs without an issue. I built it this way with the tubs closer together and using 2x2s for them to slide on instead of the usual rungs that the lip of the tub sits on. I feel with these tubs it is sturdier this way. The unit itself is very sturdy and needs no braces. And yes the bottom tub is actually on the floor. Seeing how I live in south FL, I'm not too worried about the cold lol. I am prepared to if need be in a few months or however long that if this doesnt work for me I'll sell it and build the standard concrete tub shelf. I'm just one of those people who has to try out their new ideas first. Sometimes they work, sometimes they don't haha we will see with this one lol.