I've just been reading some of the old threads on pondless waterfalls, and still I have some questions. We used to have a very big pond in AZ, but now that we have downsized in CO, I want to re-do a small pond that we inherited here. I don't wish to have fish anymore (too hard on them, too expensive in the winter, too much maintenance...), so we wish to convert this little pond into a more natural pondless (and fishless) waterfall. It will be small, not much bigger than it currently is, but we're using native rocks (we have TONS!) So, my questions are: do I need a filter if there are no fish? And what size pump do you think we need?