Wanted to make one comment.
Evolved: I printed out your wrasse write up years ago. Its great, and concise. I used it in the beginning to understand which types needed sand, and which did not as I have a bare bottom tank. Well years ago my sand had solidified and essentially became bare bottom. I removed the concrete chunks 2 years ago.
The one point I wanted to make is that in a large tank, 6 lines are not at all aggressive from my experience. When I say large I'm talking my tank specifically (darn near 700 gallons display) I know that goes completely against what people have observed in smaller tanks. My 6 line is way too busy cruising rockwork to notice the fairy and flashers that tend to spend more time in the open water.
I'm not saying the 6 lines are not aggressive. I just wanted to state that if the tank is large enough, mine at least, pretty much ignores everyone else as hes constantly busy looking for flatworms, and other tidbits.