Neetroplus nematopus are another ounce for ouncer. Supposed to be even more aggressive than Convicts. They are small, They are predated on by Dovii in their natural environment.
I would say a Convict was as aggressive as a Devil, they just havent got the size to really do any damage to larger fish.
I have a Jaguar that thrashes at the glass every time I go near the tank, He also attacks me when I stick my arm in the tank.
I have a Texan in a 120, still a juvi, but is a good 8" long and quite big. He is a big jerk. He thrashes at the tank sometimes, and has eaten 2 of his smaller tank mates. They have a good reputation for being mean Cichlids. This one isn't nearly as bad as I expected though, he is pretty slow so the other fish can easily avoid him...
Ounce for ounce, pound for pound, I'd have to go with the Convict. They may not be huge. They may not be exotic or rare. And, they may not be the flashiest, toothiest, most impressive of cichlids. But they have the attitude of an axe murderer on a bad day.
I thought this thread is all about the aggression but not about the size. Some of fish mentioned in this thread are just big and predatory but not necessarily aggressive. I am sure a docile blue whale can kill a tiger if the whale somehow lands on the tiger, but it does not mean that the whale is aggressive.
From what I've personally experienced....Amphilophus festae is one of the more aggressive species. It seems though, that if you have enough tank space and enough fish to distract them, they can be kept with other fish. So its really relative to your own opinion I think. This is really a rather frustrating question cuz everyone seems to think they are right and no one is ever gonna really agree to one cichlid being the most aggressive. Granted there are several cichlid species out there that are indeed rather aggressive, but i don't think we are ever gonna know which one is the most aggressive. Stupid blue whales...don't they know Tigers are endangered?!
All I know is my Red Devil left only the head of my once 6" Green Terror. Nice of him isn't it. Not to mention the Red Devil also eat my oscar the next day for dinner.
I go with RED DEVIL all the way. He hunts for fun.
I also agree about the green terror be a little puss.
I was trying to cause problems.....I had a Red Terror, Green Terror, Texas, Dempseys, Parrot, Oscars, Pleco, Asian Red Tail Cat, and a RED DEVIL all in the same tank a few years ago. The RED DEVIL was relentless, went after everyone except the parrot for some reason. Eventually I had to get rid of the devil cause it was keeping me up at night thrashing around the tank. Of all those fish mentioned above....the dempseys and the parrot are the only ones to survive the wrath of Dave the Red Devil.
I just bought a juvinille Red Devil, but he has his own tank for now.......My other fish are nervous just knowing he's in the house...hehehehe.