Really nice scape, but you need some aquascape epoxy (I like D-D brand), or just some JB Weld. Get some and push it into all the joints. You'll be sorry if you don't, especially if you get an urchin.
My one critique is that the top left pinnacle and arch are really close to the surface. If you put something there, it will be up to the top of the water in no time. Aquascape for what you will want a things to look like year or two from now.