I don't understand why so many people think its best to have nothing on the bottom. First of all, it looks totally ridiculous. Second, it has no ability to retain moisture. And third, it makes it harder to clean. I've been using reptile carpet and it works great. It can hold lots of moisture and still dries out between misting. It stays fairly clean by just picking any debris off it and if it gets dirty just give it a quick scrub in the tub and it comes out good as new.