I just added one to a similar setup but don't have the six line. My hawk has completely ignored it as have all the other fish. The only one i was really worried about was my Starry blenny as i've read plenty about these two species going at it until one dies. It is a large midas which i think has helped but there was no aggression from anything. Midas are shrinking violets, they can hold their own and if its just one fish that will be causing agro, i'd be tempted to try and just keep an eye on it. If its all of them i wouldn't add it.