I think a tomini tang would be good for your size tank, 75g? Mine kinda minds his own business, friendly. He's quite regal in his looks, although hard to appreciate from pics on the net. I've had a copperband as well, and they got along quite fine. I also have a baby vlamingi tang, which I wouldn't recommend for your size tank, but have to say that he is the most docile tang I have ever seen.