Love your 220 scape. We'll see how this one turns out. I think plenty of caves in the left structure and especially the center one. I built the rock work in the tank (without sand). The one thing I would change is I got anxious and when I pulled the center structure out to cement it (Marco e-400), after gluing it, the top portion fell off. So I tried from best of recollection and pics to duplicate it and it ended up WAY too high.