Festivums should have a minimum of 30 gallons for there tank and like to have larger.They like to be with others but dont really need to shoal.They like some hiding spots,will eat small fish like neons and guppys,and are good tankmates with nearly any fish that isnt too small or too large, ive kept them in an aggresive,semi-aggresive and peaceful cichlid tank and they mainly stay at the top of the tank.
HTH
DD