nice coral, some kind of tri-color im guessin??.... sometimes ill just use epoxy or alot of super glue gel the Duro brand type seems to work the best IMO very sticky underwater.... i have to use awhole tube on some of the larger pieces but ive found it over at the depot for like $2 for a double tube pack....
try to get the piece secure cuz acros dont like to be messed with too much or they start stressin out and u have a higher chance of somethign goin wrong...