We've had a gg now for about a month something had a go at it on the first night and damaged a fin, the night after it fought back and it finished off 2 silver sharks (about 6yr old) and one of the silver dollars. Its now fine and as long as the other fish know who is boss it rarely has a go at the others, it never touches the kissing gourami in there.
Changed jobs about a month ago and there is a little aquatics shop near there, I went in to get some treatment for the damaged fin and he's got two of them, here's a pic: