Use the superglue gel. Take the frag out of the water and get a frag plug or a pc. of rock rubble. Dry them both at the point where you want to glue them, put the glue on the frag. place it on the rubble and hold for 30 seconds to a minute. Rinse off in a cup of tank water and place back into the display. Don't worry about having the frag out of the water for up to two minutes.