For me it's been Hemichromis Fasciatus. So far killed 5 dovii's, 1 jag, 2 convicts, 1 salvani, another 1 or 2 more. I quit buying fish and now have a pair that just took my whole 75g at 3.5"... If you go to the hemichromis fasciatus thread below you can see him in action a little bit. has 3 dovii's cornered and is chasing the hell out of a red devil almost twice his size. So far, this has been the most aggressive fish that I've kept.