In my experience, it is not a good idea. Sixlines will generally destroy any other Pseudocheillinus species. I have had them in very large tanks, and even with several thousand gallons, it didn't work. If you can find a TINY one and house it with larger conspecifics, you could try it, but I don't think it's a good idea. I'd just pick the one you like the most, and go with that. Maybe someone else has had luck, though.