Most of that structure is glued together. The pic was taken shortly after I stocked it with 3 juvie Labidochromis caeruleus (yellow labs) and three Aulonocara sp. (peacocks), but they were in their hiding stage so you can't see them, 'cept for the yellow blur in the center of the tank. The rocks are not actually on the sand itself, but are on eggcrate placed on the bare bottom, and the sand spread around the rocks after they were in place, so that any digging by the Africans would not disturb the rocks in any way.