I'm surprised no one has brought it up yet, but there are hybrids of Andinoacara pulcher and A. rivulatus. They are often sold in a lot of stores as blue acaras because at smaller sizes they display more pulcher characteristics than rivulatus ones. The hybrids tend to end up at pulcher sizes, but with rivulatus aggression levels (though they sometimes end up exactly the opposite and everywhere in between). Definitely a fish most often best kept with more aggressive cichlids.
Based on the pictures, I'd say you have such a hybrid and it explains why there is some confusion.
