well first i have a 200g tank and it holds a female red terror.7inch...a silver aro.17inch...a gold flake oscar.9inch...a red devil.5inch...a chocolate pleco.6inch...and a wild blue gill.5inch...
I wouldn't add any other cichlids in there due to possible aggression, eventually the oscar might not be able to hang with some of the more aggressive species you have, but that of course depends on individual fish