Essentially, "green terror" is a nickname that applies to either species of Andinoacara (former Aeuquidens). Some people insist there is a "true" green terror and a "false" green terror, but this is something of a contrived hobbyist argument without much scientific relevance. The real question among experts over the years was which was the true rivulatus, some older books and articles saying what is now stalsbergi was the true rivulatus, which turned out to be opposite current classification.
Stalsbergii are more rare in the trade, and the people who suggest it is more aggressive than rivulatus, typically own wild caught specimens, or F1s. I've seen several Rivulatus that were downright nasty at the same time.
Same fish really, same temperament and habits. They both grow*really slow and are shy as juvies don't really start showing attitude until they get bigger.
Jesse
