a standard 55 wouldn't even keep an oscar for life... they are simply just too narrow. 55 gallons of water is fine, but it needs to be with different dimensions.
i kept an oscar regular jack and a male con for three years in a 55 with no problems but maybe i was just lucky my oscar only hit 11 inches and my jack 9 but my convict got massive it was like 6 inches but i also overfilterd and did daily water changes so i think u could try it
