One of the wild locations for sveni is the Yacyretá reservoir in the Paraná river, they don't need big current, just clean water and sufficient oxygen. The true rheophilic geos tend to be sleeker bodied (as you'd expect), like agyrostictus and taeniopareius, not the higher bodied species like sveni, atifrons, etc. As I've posted here a number of times, note "the Geophagus habitat in nature" section of the video guide linked below. Typical habitat is "fast moving rivers." However, "usually, the high bodied species occur along beaches in the slack water zones and the more slender species are rheophiles that live directly in the rapids."
Geophagus - Guide to Amazonian Eartheaters - nearly all Geophagus species !
I've seen the argument that few aquariums pack the current of many of the SA rivers and what we think is plenty of current would be mild for many rivers. True enough, but in practice in an aquarium, excepting the truly rheophilic geos, they're not fussy over current as long as O2 is sufficient. I've also posted the video below here, a perfect example of what Oliver Lucanus says, altifrons in quiet water along a beach.
Geophagus Altifrons (Eartheater Cichlid) in the Wild
I've seen 11" sveni, occasionally more, but I wouldn't call it typical, they're often 8-9 inches or so. I've seen fishing photos in their native location and they were more like 8" and chunky. Like a number of other fish, max size is not necessarily their typical size. G. altifrons are a species more commonly reaching 11, 12 inches, sometimes more. In any case, no matter their size, from my experience with sveni a 5ft tank should work for an adult pair and the right and not too many companions.
Possibly a small group of the right gender and temperament mix, but I wouldn't guarantee it.
