Actually Apistogramma are in the Geophagine subfamily. They do have the modified gills of the subfamily, they just aren't as developed as Satanoperca or Geophagus, but still more delevoped than Guianacara and Acarichthys.
Well they are at least until DNA studies are done. Traditionally all species with the modified gill arch were subfamily Geophagine. But DNA evidence has added one genus that doesn't have the gill arch (Guianacara) and removed one that does have the gill arch (Retroculus).