I read on here that it was a good idea to put stone under the water bottles, one to catch the drips and two for the piggies to keep cool - well they certainly appreciate it as you can tell by the pigture!
I use two tiles, one is marble and the other granite and they love them also.Although I like the look of what you have better mine are just two squares randomly in their cage. I an believe I didnt think to put it under the water bottles though it all seems so obvious now.