They grow somewhere around 1/2-1 inch per month and cap off around 6 inches, so that should be fine. 30 is technically their minimum tank size, but they would definitely appreciate the upgrade.
i wouldnt put a pair in a 30... blue acara can be pretty rough on each other. solo cichlid just fine but not a pair. my pair (regular color not electric)is in a 4 foot tank and even then if theres no other large fish for them to target as a pair she gets pretty beat up.View attachment 1436956