The simplest thing you can do is purchase a submersible pump and some tubing. That's what I have... ummm, I'm still trying to get it to look like a proper waterfall though. I have the water pumping up, but getting it to flow downward in a nice looking flow is the problem. So far all I've been able to create rain, a fountain and right now, I have a wall of water that comes down on one side... I may do more with this idea as my WTF likes to sit by it.