Six line's can be a pain but I've never had one that was a problem. My current frag system had one lonely six line all by himself until my clown started picking on my Splendid Dottyback. The poor thing was all banged up and on death's door when I was able to scoop him up with my hand and add him to my frag tank. That was on August 30th of this year and you can sometimes find the six line and the dottyback hanging out. Seriously. It's almost like they school together. They've got the whole tank with plenty of rock and they chill right next to each other most of the time, very odd.