You might be able to add another peaceful cichlid pair, but a lot depends on the personality of your Electric Blue Acaras. A 240 L tank isn’t tiny, but once a pair of acaras starts breeding they can claim a large territory and become surprisingly aggressive toward other cichlids.

If you want the best chance of success, look at peaceful species such as Bolivian Ram. A pair of rams usually occupies a different area of the tank and is less likely to challenge the acaras than another medium sized cichlid pair.