Volume of Water Removed from Rectangular Fish Tank

Lucas has a fish tank shaped like a rectangular prism. The dimensions of the tank are 3 feet in length, 2 feet in width, and 2 feet in height. He fills the tank with water completely. Then he removes half of the water to use for his new aquarium setup. What is the total volume of water in gallons that Lucas removed from the tank? (Note: 1 cubic foot equals approximately 7.48 gallons.)