Make three Styrofoam cubes. The first cube should measure five inches on each side, the second cube three inches and the third cube two inches. Cut the cubes from a large block of Styrofoam using a saw or knife with a serrated edge. Avoid using a knife with a straight blade since it can flatten and deform the Styrofoam.
Attach the three Styrofoam cubes with waterproof glue. You can purchase this type of glue at your local home improvement store. Set aside the cubes and let the glue dry according to the directions.
Spray paint the cubes with your favorite color. Use only water-based, latex spray paint. Avoid using other types of spray paint as they can destroy the Styrofoam over time. Set aside the cubes and let them dry for several hours.
Spray paint about two cups worth of Styrofoam peanuts. These will be the "rocks" for your fountain. Spread the Styrofoam peanuts on a large sheet of wax paper and spray paint them directly. Let them dry for several hours.
Drill a hole through the cubes from the bottom, making sure a hole is also created at the top.
Insert one end of an aquarium pump tube into the hole. Push the tube all the way up until it comes out the top hole about 3/4 of an inch. Connect the other end of the tube to a small submersible aquarium pump.
Place the pump and the Styrofoam cubes into a decorative bowl or plant pot.
Pour the Styrofoam peanuts into the bowl, covering the pump and half of the lower cube. Add plastic flowers or miniature figurines to further decorate your water fountain.
Pour enough water to cover the submersible pump. Plug the cord of the aquarium pump into a wall outlet and test your new Styrofoam water fountain.