big nasty things, love them,
http://www.seriouslyfish.com/species/geophagus-brasiliensis/
all accurate as far as I know, but they can get to around 27cm if very happy
best to set up a species only (or large SA cichlid tank) minimum 1500x45x45 (deeper and wider is better)
expect them to dig any form of substrate so a fine smooth sand is best, be careful of large rocks as they can undermine them and send them crashing into the bottom of your tank. lotsa driftwood and hidey holes is best.
treat them like a particularly nasty Surinamensis type geo and you should be fine