[cypher]

Which cage do you have?
If water is on an upper level only accessible via the tube you simply can't resolve the issue, most hams will block tubes at least some of the time & you can't stop them.
Water needs to be easily accessible at all times.
Ideally you want a cage with one large floor space then optionally a shelf or two that they can easily climb onto either from the substrate or using something like a bendy bridge so you may want to have a think about getting a different cage unless you can remove the tube & make access easier.