I tried one of these once and they are VERY territorial. He picked on my severum mercilessly until I had to separate them. I tried reintroducing them later, but he went back to the same thing until the sev finally fought back and the brasiliensis lost. I tried again with a "Bahia red" geo (very similar to the brasiliensis) and he has been getting along fine (that is since he killed his own mate, which I wouldn't consider getting along).
Thanks everyone!!! So he's a Geophagus sp. brasiliensis! Nice! My next question is... does anyone know where I can get a nice female for him? He's about 8", so I don't want the female to be too small.