my GT is the opposite, so docile its not funny. When seen him in the shop and about 3.5inch he a bump on his head and was guarding a rock and flaring up at any fish that came to close, looking back he was prob breeding with a female in that shop tank. When i added him to my tank with an syn and a jd who were both a tiny bit larger then him he became the least dominant fish in the tank and his hump dissapeared with in a week...JD being the boss and the syn never liked the gt. 2 months later, jd is still the boss, syn still dosent really like the gt and Syn in now the biggest. Gt colours and still pretty plain, hump never came back and never seen an ounce of aggression, never once has he stood up for himself. I thought he was going to be a bit of a glassbaanger but he his quite timid.....be interested to see if my gt develops an attitude like yours with age?? a mate used to have a gt and just like yours he have attitude from a very young age alone with great colour and big hump, it never killed any other fish but was always the boss