by the time you fill the tank with the necessary rockwork to maintain a proper group (1 male + 4 females) of Labidochromis caeruleus you're going to have only about 30 gallons or actual water. yellow labs grow to about 5 inches and five of them will in my opinion, fill a tank containing 30 gallons. moreover, African cichlids require HARD + ALKALINE water while barbs do best in softer, acidic water.