Well, I am not sure about the plant and the water change, I just know what works for me. I have talked to several people that have the plant/vase setup, and they said that they don't have to change the water as much either.
I might get a vase/plant when the weather warms up. Not sure if they are easy to find now.

If anyone wants to get a plant/water lily word of warning. I had a difficult time cleaning out the roots. It takes some work.