gel super glue works fine for me. i take the rock and frag (usualy attached to small crushed coral) and dry off the ends that will be glued. i dab on some gel super glue and stick them together for 5 seconds and place into a bowl of tank water for a few mins and place it back into tank. i went crazy and glued a ton of mushrooms and peices of macro algae to a rock and everything went fine, the mushrooms moved off their tiny peice of crushed coral and attached to the rock just fine. i have not noticed any problems with useing super glue in the tank, dont use the glue on live tissue because when it cures, it produces heat. plus when you put the frag into water, it sorta instant cures.