Originally Posted by f14peter
Most LFS or e-shops have aquarium epoxy, which is great for helping steady rock formations.
Mix up a wad, then press it in where rocks come close to touching, kind of like adding some rock where you need.
This is definately the best way to do it. It secures the rock together and i also use it to place corals onto the reef. ANd, if you decide to change it you can also buy the marine glue un-doer. In case you want to move the LR or something.