Sorry but those are not satanoperca. They look to be either geophagus steindachneri or geophagus pellegrini
^ Can you tell me the reason why you have drawn that conclusion? Which one the geophagus steindachneri or the geophagus pellegrini do they favor more?
I think Ryan and Orinocensis are right. I was only looking at the pattern, not the whole fish. The face is much too rounded to be a Satanoperca. Juvy "Geophagus" pellegrini and G. crassilabris have a similiar pattern and there face fits that group more.
This is why I dislike ID'ing, I tend to focus only on one diagnostic and not the whole fish. Sorry!
I wil take a guess on geophagus brasiliensis...