Zoanthids and star polyps do not glue well and will come off. They are soft and flexible and hace a slime coating so the glue does not adhere.
reefcrazy had some good suggestions to get the frags to adhere naturally to a piece of rubble. I also put them in a smal bowl of tupperware type container with some rubble so they become attached on their own. Other options are to rubber band then to rock rubble, stick a toothpick through them and stick it in a crack in the rock, loosely tie or wrap a piece of netting or wedding veil tule fabric around a piece of rock with the zoas inside. All work well.
For LPS and SPS frags I use medium body super glue mostly, sometimes AquaMend epoxy and sometimes even a mixture of both for hard to place situations so it sets up fast but permanent underwater.