Six lines are very active swimmers and I think that is what is very attractive about them. I, myself, also had a bad experience with one. IMO, they need to big (125+) to have enough room to swim and not be aggressive. Many have had them in smaller tanks, but it runs a risk. I can only imagine the pain it would be to get one out of a 75.
I agree. I think six-line's are misleading fish due to their relatively small size. They are extremely active swimmers, which is what makes them fun, and they need room to really express that.