Hey! I have a six line. It's my favorite fish for sure. I kept him in a QT with two yellow clown gobies for about a week. The six line hovered around all day poking at the live rock and didn't bother the gobies at all. I added him to my 29 gallon tank which had 4 ocellaris clowns, two firefish, and a cleaner shrimp.
At first everything was fine, then I found some aiptasia and moved some of the live rock to my QT. Both the firefish and six line like to sleep in the sand, so when it came time to find a cave, the six line would chase the firefish out of the only suitable spot. I've also seen a brief, 5 second exchange of nipping between the six line and one of my clowns. I read that six line wrasses sometimes act as cleaner fish and will pick at parasites, so maybe this is what he was trying to do and the clown didn't like it.
My six line is very peaceful now. Even though i have a small tank, everyone gets along as long as they have lots of live rock and a place to sleep. One bonus perhaps, my firefish don't hide in their boltholes nearly as often now. They still sleep right next to the wrasse, but during the day, maybe there's some territory squabbling that I'm not aware of.
Make sure you see hundreds of copepods in your tank, or even consider seeding with more pods before purchasing the fish, because they won't survive on flatworms alone. Mine eats frozen mysis and brine no problem, but it is a really awesome fish to watch as he's hunting for food. I think the neatest part about the fish is its eyes. You can watch them move like little security cameras, and you can tell exactly where the fish is looking and when he's about to strike a copepod. Also, I haven't been able to capture it in a photo but he has a bright orange dorsal fin that looks really intimidating.
Good luck! I want two six lines, but I'm 100% positive that that will cause some aggression.
