Jeff, in all honesty the bubble should be in the substrate. The high light corals need to stay way up there. Glad you found the little frag. Superglue Gel or epoxy will work just fine. Just make sure to not get the gel or epoxy all over--just the bottom of the frag. A dot'll do it. ;D It seems when people first start a salt tank they buy a ton of rock and then later learn that it's blocking flow from moving around the dt. When I decided to do a minimalist aquascape I simply put some of my rock in the sump. I can only say what I would do and that's to completely change things around. You'd be surprised at how much nicer your tank looks when you eliminate the "rock wall" look. Just MHO, nothing more and nothing less.