For hard corals if you use the super glue it will take 10 to 15 minutes and you will need to be careful not to damage the coral during this time, if the frag is larger you may want to use an aquarium safe underwater epoxy cement. for soft corals you can use a rubber band, or other item to hold the coral incontact with the rock or hard item you want it to attach to. do not glue soft corals. hope something here helps.