I've had an Opaline Gourami that's thrived in my tank for quite some time now. It's lived peacefully with other fish, and hasn't acted aggressive at all. Today I bought a Pink Kissing Gourami. They're both approximately the same size. Immediately upon adding the Pink Kissing Gourami to the tank, the Opaline Gourami has changed colors and has become very dark. There was no aggression between the two fish; in fact, the Pink Kissing Gourami seems completely oblivious to the Opaline Gourami. The Opaline Gourami usually spends its time in a certain part of the tank (and it is not territorial), and since the Pink Gourami has started to stay there, it seems to have been keeping out of its way for some reason. I've read threads and forums, and most color changes result to either stress or mating. I believe that the Opaline Gourami is a female (it has a more round, small dorsal fin) and the Pink Kissing Gourami is a male (it has a longer, more pointed dorsal fin). It'd be of great help if somebody could help me with this.