A feat so amazing you would think it's impossible. Even more amazing, it's easy and cheap. This gorgeous waterfall actually isn't water at all, it's sand. Using the same principles of physics that make bubble filters and Alex Andon's Desktop Jellyfish Tank work, this feature uses air bubbles to push water up a pipe to the top of the aquarium, creating a sort of vacuum to carry sand up to the top.
This project will only take a few hours to put together (depending on how much experimenting you do) and most aquarium hobbyists will have some of the parts lying around. I completed this project for under $50.
Step 1: Materials
A tank (obviously) Under $20 at thrift stores.
Length of 1" PVC pipe about the height of your tank. ~$4
2 elbow joints ~$2
An air pump (I used a Whisper 60 for this 10 gallon tank) $30
Air tubing ~$2
1 air stone ~$2
A bag of sand (A fine grain, but too fine and it will cloud your tank. I got mine from Fred Meyer. White looks the most like water) ~$5
Rocks for a natural look Free- $20
A plastic water catcher tray ~$2
Step 2: Assemble the Pump
First, cut your PVC pipe to length, about 3 inches shorter than the height of your tank to allow room for the elbows. For my standard 10 gallon tank, this was about 8 1/4" (21 cm).
Now drill a hole in the top of one of the elbows, the size of the air tube. Then thread the tubing into it. This will be the top of the pump. Fit this onto the pipe, making sure that the air tube goes all the way through to the other end.
Attach the air stone to the end of the tubing, and fit the other elbow onto this end. The air stone should be at the bottom of the pipe (see pictures for details).
This is now a completed pump. Just attach the air tube to your air pump and submerge it underwater, so that the top half of the top elbow is out of the water. You should see that the water starts to flow.
UPDATE: The current may cause sand to shoot out of the pipe and spread throughout your tank. To fix this, I took a piece of fiberglass mesh screen, and glued it around the opening of the pipe so that it makes a U shape in front of the pipe. This blocks the sand very well. I used just a dab of aquarium grade silicone on either side of the pipe and wrapped a strip of the mesh around it. Sorry if this sounds confusing, see the last two pictures for better detail.
Step 3: Collection Basin
The sand has to go somewhere, and there are many ways you could do this, but here is my solution.
Cut about a third of the water tray around the edge (if you're putting the waterfall in the middle of the tank, cut it in half), leaving about 2 inches of plastic around the base. Place this in the corner of the tank as shown in picture 2. Now place rocks around the edge to hold it in place as shown in picture 3.
Now you have a nice place for the sand to gather to be collected again by the pump.
Place the pump in the corner and fill the area with sand (Pic 3 and 4).
This is when I took the time to fill the aquarium to test it out (Pic 5).
Step 4: Stacking Rocks
I placed a couple of small river rocks in the sand on either side of the pump to provide a stable base to start stacking rocks on. The rocks I used was some basalt I had lying around. Whatever you can get your hands on should work, so long as they're somewhat square. Stack them all the way up to the outtake.
Sorry I don't have any pics of me doing this. But you're very clever. You can do this.
Step 5: Decorate!
Add some gravel to the rest of the tank. I chose to go with brown pea gravel, but anything will do. Make sure to make it deep enough to cover the plastic tray. Or don't. Aquariums are art, so you may do whatever your heart desires with yours.
I put some Java Fern in between the rocks as you can see in the picture, and on the other side of the tank I banked up the gravel and put in a few more pieces of basalt, as you can see in the video in step 1. Other plants I used are Staurogyne Repens, Water Wisteria, Amazon Sword, Willow Moss, and Cyprus Helferi.
That's it. You're done.
Step 6: Tips and Tricks
Check out the pictures above for inspiration
Also check out these videos:
Some additional things you might try:
You might be able to hide your heater and filter behind the rocks if they are small enough.
Create a custom rockscape for your waterfall to flow over using methods from these Instructables.
White sand looks the most natural, but you might also use colored sand for a visually striking waterfall. Florescent sand under a blacklight light can make your waterfall GLOW!
PLANTS PLANTS PLANTS!
Use another pipe to make a wider fall (Pic 4).
Try using an elbow with a wider mouth at the bottom for increased flow.
If you liked this project, please vote for it in the Aquarium Contest.