I currently have my GT in a tiny 10 gallon tank with two other cichlids. He's only 2.5 inches long. His tank mates are a 2 inch Acaei Cichlid and a blue African cichlid, the kind of which they usually sell as "assorted" African. The "assorted" African is by far the most agressive fish in the tank. He constantly bullies my Acaei. The GT is very peaceful. He never bothers the other fish. Occasionaly the little mean African will get a little bold and the GT will stand his ground and drive him off, but nothing serious.
I know my GT is a baby still but I'm hoping he stays peaceful like he is now. He's actually pretty shy..