1 cu/ft in a 7.48 gallon100 gallons of water / 7.48 = 13.4 cu/ft

There are 750 bio balls in a 12x12x12 box = 1 cu/ftIf the entire 100 gallon stock tank is filled with bio balls it will need: 750 bio balls x 13.4 = 10,050 bio balls.