I have one with a clarkii, green clown goby, and a starry blenny. He gets along with all of them just fine, but I tried moving my rainford goby to that tank and he harassed the heck out of him. Never pays any attention to the shrimp/crabs.
I had a 6 line. Previously the only fish were 2 clowns and a goby which had been in the tank for a few months. There were numerous snails and crabs along with 2 peppermint shrimp.
I added the 6 line, 3 bangai cardinals and a firefish.
The 6 line was aggressive toward all the other fish but specifically the firefish even though at the store they were in the same tank. The firefish only lasted a day before I found it dead. But in that day the 6 line was constantly chasing.
The 6 line lasted a week before it decided to fight a power head and lost. I never saw the 6 line go after the shrimp but it was definitely aggressive. They are gorgeous but I won't add another one to a community tank.