Though most young cichlids are very different than adults, I find it quite interesting that argentea are almost carbon copies of adults at a very young age.
While young they can be fairly docile in a community setting, but once they hit about 5"-6" (and they become large, 14" are not uncommon), males can become hyper-dominant, and need large tanks (250gal +) because any similar size and appearing fish (especially cichlids) tank mates are at risk of death.
If you get a compatible pair, a 180 is a possibility, but I believe the tank would only be large enough for just the pair, and maybe some dither fish.
By the way, I see you are from Sri Lanka, a place where one of my favorite cichlids is endemic, Etroplus suratensus.