Things You'll Need
- 2 pieces of polystyrene, 59 inch by 21.65 inch each
- 8 to 10 fist-sized pieces of polystyrene
- 1 tube of nontoxic aquarium silicon
- Sharp carpet knife
- Heat gun
- Concrete, 11 pounds
- Concrete color, 1 cup
- Gloves
- Mist bottle
- Paint brush
- Cloth
- Salt, 2.7 pounds
Instructions
Glue the two pieces of large polystyrene together, back to back, with nontoxic 100 percent aquarium silicon. Glue the eight to 10 fist-sized pieces of polystyrene to the existing double-thick piece of polystyrene so as to form small raised areas.
Hack the large sheet to create holes and ravines, and shape the fist-sized pieces of polystyrene to resemble rocks.
Use the heat gun to melt and smooth the entire polystyrene sheet, including the raised rock features.
Mix up the 5 kg batch of concrete. Add the color slowly until you have the desired shade. Using gloves, smear sufficient concrete to allow you to cover the entire front "face" of the polystyrene background with a thin layer.
Leave the concrete-covered background to dry for 48 hours.
Use the paint brush to splash the remainder of the concrete color onto the background. Spray a sufficient mist from the bottle so that the colors begin to run.
Use the cloth to rub the color onto the background to imitate the appearance of natural rock and leave the background to dry for 48 hours.
Soak the background in a solution of 8.8 ounce salt to 2.6 gallons warm water and leave overnight. Repeat the process three more times, using a fresh salt solution each time. The artificial rock work can now go into your aquarium.