Originally Posted by nicetry
Who told you your rocks should go on the glass and not on the sand? That's simply a matter of preference. As for the sixline, the pseudocheilinus wrasses do not burrow in sand but will hide in the rocks at night. It won't be an issue.
The New Marine Aquarium by Michael S. Paletta advocates adding the rock first and then the substrate in chapter 4 pp 77-79. Also, this is the generally accepted method that I have read here. Not trying to argue, just trying to say that I believe that rock should be placed first. That being said, I think you shouldn't worry about a 6-line knocking over your rock. You should make sure all of your rock is stable by touching it and evaluating for stability.