I have never done so though I have fantasized about it from time to time. (My main problem is the amount of space even a modest waterfall would take up. My plants already fill the tank. Anywho...........)

If you use the search function on this forum you will find lots of threads dealing with water features. Post a pic when you get yours up and running!

Hi
I used expanding foam in both a 75 and 150 gallon
standard aquariums. The 75 was actually a paludarium
150 used a false bottom . Took a lot of trial and error to keep the water from splashing on the glass.. Streams were even more difficult ,containing the water .
false bottom runaway the best.. I used a canister filter for the power, plumbing was PVC under the foam
Used acrylic paint to alter the color of the foam
Though the 75 has returned to an aquarium the "waterfall" now serves as a background. Has been running since 01 with only minor problems.
The 150 got some frostbite this winter but will be returned to a terrarium come spring. WITH a reliable heating system !!! lol gary

I decided to go with Cork Bark background since its all natural and wouldn't take up much space. The tank is only 10g. I slanted the cork a bit for the W'fall. It should look more jungle tropical once the plants grow some.

can't figure out how to add a photo on this forum...

You can always use an old water pump from those ZEN tabletop fountains. I see them in my thrift store all the time. I use Expanding foam (right stuff). its non toxic when it dries and you can shape it into anything you want. I stuff netpots into the foam so i can have things hanging off the back wall of my terranium. Also you dont need more then a gallon of water for a water effect. I use 10g tanks all the time and always get awesome results.