Unfortunatey, there is absolutey nothing that you can do about it, so it would be best to learn to not be so bothered by it...If I spent good money on a dive trip, I don't want some chuckleheads constantly banging on their underwater wind chimes.
BTW - i only have 50 dives so far, but I have NEVER been on a dive where there was constant tank banging - and the little banging there was has usually been the DM/guide attempting to get the attention of his group.