I believe it is basically to reduce the chance of an avalanche killing fish, breaking or scratching glass/acrylic. The best way to stick live rock together seems to be superglue. Check out nano-reef.com, they have lots of detail on this. Apparently the superglue (cyanoacralate sp?) forms a shell quickly upon contact with the water and does not pollute the water at all. Some of these people attach frags with super glue also. I haven't done this as I am still in freshwater, but I do a lot of lurking in the marine sites. Hope this helps.