What are the most redpilled tropical aquarium fish?

My friend's dad donated his fish to me, including a large gold gourami. I noticed it began harrassing the four Pearl gouramis I already had in the tank (65 gallon tropical freshwater). Curiously, it ignores all of the other fish: six (formerly two) glass catfish, two red skirt tetras, and an unidentified pleco-looking fish.

Am I witnessing some sort of fish race war?