So back in the day I had a 46 gallon with a six line that was the least aggressive out of most of my fish. Now I have a 29 gallon and would love to get another yet everyone keeps telling me how aggressive they are. In all of your past experiences how have your six lines been? What have they been in with? What size tank? Mine is a 29 gallon and I would add it last with a clown, flame angel, goby, and cardinal fish preceeding it.