When using superglue,it is helpful to accelerate the drying process. First, dry off the surfaces to be glued by gently dabbing with a paper towel; the glue won't grab if a film of water is present. Second, after placing a bead of glue on the plug or rock,dip it inwater( I use tank water) for 15 to 20 seconds. Third. place the coral on the glue and give it a quarter turn twist and hold it in position for about 20 seconds. Should be good to go. I would position a larger colony on rock and perhaps putty a few smaler pieces of rubble in to hold it in place.