Are you using gel type super glue? Liquid is hard to work with, but with gel what I do is put a nice little bit of it on the frag plug, I then dip the wet super glue into a small container of RO water. This will cause the glue to haze a bit. I then quickly put a second equal sized amount of glue on the frag then I put that in the tank. When you place it on the rock, twist it a bit and hold for about 15 seconds. It should hold quite nicely.