The 'True Green Terror" Stalsbergi are much more aggressive then their 'False Green Terror" Gold/White Saum brothers.
Probably what you've heard, read on some forums or maybe even the occasional article repeating common wisdom, but it's wrong. Stalsbergi as the 'true' or 'original' green terror is a common misconception. As a hobbyist nickname that's been applied to either fish, with nothing official or scientific about it, the idea of a "true" and 'false' green terror is more or less artificial, anyway, but:
The basic order is: White edged rivulatus (Ecuador) showed up in the hobby first in the 1970s. Soon, also 1970s, came wild collected gold edged rivulatus. These were given the nickname "green terror" . The question at the time was: Are they
rivulatus? Meanwhile there were also photos of what are now stalsbergi circulating. 1982-- a German article called what we now call
stalsbergi (Peru)
'the green terror that isn't', being a third fish, different from the white and gold edged Ecuador fish originally nicknamed 'green terrors'. So, if you correctly know which is now stalsbergi and which is now rivulatus,
stalsbergi was "the green terror that isn't". However, the real question was
which is the true rivulatus? Time has confused things and some turned this into W
hich is the true green terror? but that wasn't the question.
More than one article has explained some or all of this, but one of the best is
Here, article by Wayne Leibel, biologist and cichlid expert who himself has written more than one article on the subject.
To sum up-- one reason so many have it wrong is at one time stalsbergi was considered the true
rivulatus-- not the same thing as the true green terror. In fact, some older books and articles (some of which I have or had) had photos of the Peruvian fish (stalsbergi) captioned as the "true rivulatus" and from this a number of hobbyists concluded and spread the idea it was also the true green terror (which, based on this, I also started to think at one point)
. BUT-- the Peruvian fish turned out
not to be rivulatus, so it's been named stalsbergi. The Ecuador fish is rivulatus.
There's also another similar, reportedly slightly smaller, fish from Ecuador: Andinoacara blombergi.
As for rivulatus not deserving the name? From the article I linked above: "The fish got the name "terror" for good reason, though. They were far too aggressive to pair up and spawn, even in a large tank, and the partial divider method did not work for them as it can for other large, aggressive neo-tropical cichlids." I've had wild rivulatus and mine wanted to fight everything, even at 2 inches, including fish twice and three times their size. Comparing aggression of lfs green terrors to wild or F1 stalsbergi, or to wild rivulatus, is apples and oranges.