It never occured to me that the structure wouldn't havevto be an actual pile of rocks. Marinescape ordered density EPS Foam from Universal to complete the final touches on a few of the aquarium backgrounds.
Tropical Fish Care Tanks: Here is a step-by-step guide to a Iwagumi style set up I recently did. This is a 5 gallon Fluval tank, so really small, and sits on a bookcase in the living room. I will post more pics as it grows in!