It could be a breeding ground for bacteria. I would not use one especially if your snake is prone to defacating or uninating in the water. They might not recognize it as a water source.

Also, if you are trying to make it a display cage, I recommend using a different species. This is because balls *should* be in their hides 90 percent of the time. GTPs and ETBs are much better because they do not hide. Make sure you are properly skilled before trying such a hard species though.