If they are alive now, they will all live and become colonies of their own. This is how they are fragged in the first place. There is no life inside the skeleton except for at the very top where the flesh is. I wouldn't bother trying to glue it all back together. I'd spread a couple pieces around the tank and stab the rest in the sand, and let them all get nice and healthy, then I would offer the smaller pieces I didn't want for sale.
Super glue Gel is safe. I don't know about other adhesives.