The fish tank is a hexagonal prism, since its base is shaped like a hexagon.
Each side of the hexagonal base measures 12 inches, while the height measures 30 inches.
The volume of the fish tank therefore, is given by the formula;
However note that the volume is to be given in gallons, and hence we'll convert cubic inches into gallons.
The standard rate of conversion is
1 cubic inch = 0.004329 gallons.
Therefore, the volume in gallons is, 48.5888 (approximately)