Brasiliensis are aggressive. I had four that had tore each others dorsal fins off on route to the LFs and they were apparently too many in the bag when they came in, I gave them a go and got a good reduction because of the fins. I had them 3 days and they were harrassing my severums. I put them in my other tank for 2 hours while I made arrangements to return them to the LFs and they ripped through 4 of my guppies. These were 7 cm brasiliensis and not for one second did I think they would do that To the fully grown guppies. Silly on my part but I never expected that from geophagus, especially juveniles. Almost put me off geos but I've got some surinimensis that are a joy and very peaceful.