Not many FHs go over 10" in length, 13-14" is considered a very nice size and 16" is usually un heard of, or very rare. This is because they are hybrids, and most of them consist of parrots or smaller size cichlid genes in them.
For 1 FH, I'd recommend min being a 45gallon. Perfect size would be a 65,75, and 90 gallons.
You can put them in with other fish as long as they were put in together since young and they will do well together if they were from the same batch of frys upto 7-8" in length as long as they have enough tank space and fed often to lessen the aggression.
Hope this helps,
JP