I really like the way this project turned out. When I feed the tank, I can see food floating all around, including under the rock structure. The cleaner and peppermint shrimp both like to hang out under the rocks. The engineer goby is constantly moving the sand around and the rocks DO NOT MOVE!!! The key to this project is the "teeth" you grind in the acrylic rods. It really holds the base of the rock structure in place. For the rocks that I stacked on top of the base pieces, I used nylon threaded rod and secured them in place. It takes a little work but you can set this up so that none of the threaded rod is visible and the entire structure is very stable. I was able to create lots of caves and areas where the fish can swim through to the other side. They seem to like it.