A popular waterfall feature is a "pondless waterfall". A pump is protected in a rock well, so that it can pump the water flowing into it up over the waterfall. The advantage is that bugs, algae, and frogs cannot get at the water, but the real value is that you only have to turn the feature on when you want to view the waterfall. The water is hidden in the well when the feature is not in use. When active the flow of water through the well acts like a filter and cleans the water.
Pondless stream with two vase fountains