apparently if you keep 6 or more they will school (somebody did it on another forum in his 900 gallon tank), so i guess they like company i'd get 2 anyways in that tank. they are very pretty fish.
Keeping two together is fine, I've heard that if you don't keep one or two you should get at least 6 or more. Everything I've read said they will fight until their numbers are smaller if you get numbers in between that. My tanks too small so I haven't experienced that but im sure someone on here has.