Moving from still bodies of water to dynamic, moving streams, waterfalls, etc. gives many benefits. Besides the naturally soothing sounds water creates in motion, it also oxygenates the water and creates greater visual interest.
In aquariums or palludariums, waterfalls can be easily created several ways. The easiest method is to place a submersible pump such as a power head in the water and using a piece of vinyl tubing, direct the flow onto a rock or stack of rocks that has been arranged to form a waterfall. Volcanic lace rock is very good for this because it contains interesting features that form pools, ledges, etc. and has holes through which the water hose may be positioned. With careful arranging, you can hide the hose so that the water emerges through a hole in the rock and cascades back down to the source. The rocks may be glued into position once you have achieved the result you like, though you probably will not be happy with the first arrangement you make and will want to try different ones until you are satisfied. Too much splashing will obscure the view through the aquarium glass and can make a mess, as well as causing increased evaporation and a lot of noise.
To create a free-fall waterfall with a smooth sheet of water, you must make sure that the water return has been baffled to reduce pressure. You can do this by directing the flow through small rocks or a sponge. Allow the water to cascade over a flat, smooth surface. To get an even sheet of water, the drop-off surface must be very flat and level, preferably with a straight-edged drop off. Slate works well for this, although you may use glass or plexiglass and camouflage it if desired.
A nice effect is to have a series of pools connected by waterfalls.
You may even have the falls branch into the different pools, then
return to the same main body of water. If you have room, you could
construct a stream in a large palludarium or indoor or outdoor pond. Outdoors, liner may be used by overlapping pieces. The higher pieces overlap the lower ones, leaving plenty of overlap space. Indoors, it may be best to use one piece or to construct a water-tight stream using cement and rocks.
I have seen these indoor streams and ponds used as room dividers, and
the result is truly beautiful. A good place for a waterfall or
indoor pond is in a conservatory.