Brasiliensis would be worse, they get to 12" and are the most aggressive geophagus.
Heckelli group in a 90 would probably be fine. My experience with them is that mine was a bit pushy, even with fish like convicts. So redhead Tapajos seems like the best option to me, or perhaps some of the smaller species gymo's.
Heckelli group in a 90 would probably be fine. My experience with them is that mine was a bit pushy, even with fish like convicts. So redhead Tapajos seems like the best option to me, or perhaps some of the smaller species gymo's.