If you get Vieja, (just as with an Oscar) the tank will barely be big enough for any other fish, especially as the Vieja hits adulthood.
Most Vieja get the same size as oscars (some larger, at least as bulky), and can be much more active and aggressive requiring at least a 6 ft tank.
I would consider a 90 gal a grow out tank, until any of the Vieja species reaches semi - adult.
I have kept almost all the genus Vieja and a few off shoots that once were considered Vieja.


To me no Vieja or cichlid that gets larger than 9", is small for a 90 gal tank.
The Central American genera that fit that criteria would be Amatitlanis, Crytoheros, a few Thorichthys.
Most medium size Acaras, and some Gymnogeophagus from S America also fit that bill.


