Two other suggestions ... hawkfish and dottybacks maybe?

Flame hawk:
http://members.shaw.ca/hobiesailor/a...flamehawk2.jpg
Might not initially get along with your sixline though. My sixline tried to pick fights with the hawkfish at first.. until about day 3 and the flame started fighting back. Did some damage to the sixline (bruises, nipped fins) and they've gotten along ever since. Basically the sixline will bully anyone he can... once he's discovered that everyone else is bigger and stronger than him, he stays in line.

In fact, that reminds me, yeah, I would actually stay away from a mandarin because of your sixline. My sixline killed my last mandarin, totally out of the blue and without warning. :( They got along fine until one day I found the mandarin with all her fins ripped off, she couldn't swim at all. She died later that night. :( I've never quite forgiven my sixline for that.

I can't quite get the colour to show up correctly in photos. This fish is much more pink/fuscia in real life:
http://members.shaw.ca/hobiesailor/a...dottyback1.jpg

http://members.shaw.ca/hobiesailor/a...dottyback2.jpg

No, not at all. To me, their personality is quite docile and timid really. I imagine the only risk would be if I had to catch them, I guess I'll have to cross that bridge eventually. But no, no cause for concern otherwise so far.

I'd second the dottyback suggestion. Mine took a while to come out, but now that he has, he is always out and about. You could also pick up a tank raised dottyback, that are supposed to be much hardier, like I did. They have great little personalities! A dottyback won't add to your bioload, like my foxface does. Also, my regal tang and foxface don't get along real well. The other issue with foxfaces is sometimes they can start to eat corals.