At hatching, sac fry fall through the wire basket and usually school on the bottom of the tank. Sac fry receive nourishment from their yolk sacs. In about three days, the yolk sac is absorbed and the fry turn black and begin swimming to the surface in search of food. Swim-up fry begin feeding at this stage. Sac fry can be left in the hatchery trough or siphoned to a nursery tank. Troughs or tanks must be cleaned several times per day to prevent water quality deterioration.