How Aggressive are Green Terror Cichlids? GREEN TERROR! The name gives off the impression of a killer fish that will wreak havoc on an aquarium terrorizing all other tank mates. What are the FACTS though? Is this an accurate description?Having owned somewhere between 15-20 different Green Terrors I would have to say that the name is a bit misleading! Green Terrors are actually one of the more peaceful American Cichlids. The most aggressive one I’ve ever had was about 2 inches in length he would without regard stand up to fish much larger than himself. Other than this one fish all the others were semi aggressive at the very best. These beautiful cichlids should be considered more self-defenders than anything else. Consider them to be similar to an Oscar in aggression, they will hold their own in a community tank of like-sized cichlids but don’t be surprised if you found your Green terror being bullied and chased more often than not.